diff --git a/src/am_map.cpp b/src/am_map.cpp
index c547884b2..9d8124891 100644
--- a/src/am_map.cpp
+++ b/src/am_map.cpp
@@ -845,7 +845,7 @@ static void AM_ParseArrow(TArray<mline_t> &Arrow, const char *lumpname)
 {
 	const int R = int((8 * PLAYERRADIUS) / 7);
 	FScanner sc;
-	int lump = fileSystem.CheckNumForFullName(lumpname, true);
+	int lump = fileSystem.CheckNumForAnyName(lumpname);
 	if (lump >= 0)
 	{
 		sc.OpenLumpNum(lump);
diff --git a/src/common/audio/music/i_music.cpp b/src/common/audio/music/i_music.cpp
index d190537d4..959c8aaf4 100644
--- a/src/common/audio/music/i_music.cpp
+++ b/src/common/audio/music/i_music.cpp
@@ -53,9 +53,6 @@
 #include "s_music.h"
 #include "filereadermusicinterface.h"
 
-using namespace FileSys;
-
-
 void I_InitSoundFonts();
 
 EXTERN_CVAR (Int, snd_samplerate)
diff --git a/src/common/audio/music/i_soundfont.cpp b/src/common/audio/music/i_soundfont.cpp
index 9737374fc..8edb5ab21 100644
--- a/src/common/audio/music/i_soundfont.cpp
+++ b/src/common/audio/music/i_soundfont.cpp
@@ -314,7 +314,7 @@ FileReader FLumpPatchSetReader::OpenMainConfigFile()
 FileReader FLumpPatchSetReader::OpenFile(const char *name)
 {
 	FString path;
-	if (IsAbsPath(name)) return FileReader();	// no absolute paths in the lump directory.
+	if (IsAbsPath(name)) return FileReader();	// no absolute paths in the virtual file system.
 	path = mBasePath + name;
 	auto index = fileSystem.CheckNumForFullName(path.GetChars());
 	if (index < 0) return FileReader();
diff --git a/src/common/audio/music/music.cpp b/src/common/audio/music/music.cpp
index 9664c5458..3e9202bef 100644
--- a/src/common/audio/music/music.cpp
+++ b/src/common/audio/music/music.cpp
@@ -114,7 +114,7 @@ static FileReader OpenMusic(const char* musicname)
 	{
 		int lumpnum;
 		lumpnum = mus_cb.FindMusic(musicname);
-		if (lumpnum == -1) lumpnum = fileSystem.CheckNumForName(musicname, FileSys::ns_music);
+		if (lumpnum == -1) lumpnum = fileSystem.CheckNumForName(musicname, ns_music);
 		if (lumpnum == -1)
 		{
 			Printf("Music \"%s\" not found\n", musicname);
@@ -143,7 +143,7 @@ bool MusicExists(const char* music_name)
 	{
 		int lumpnum;
 		lumpnum = mus_cb.FindMusic(music_name);
-		if (lumpnum == -1) lumpnum = fileSystem.CheckNumForName(music_name, FileSys::ns_music);
+		if (lumpnum == -1) lumpnum = fileSystem.CheckNumForName(music_name, ns_music);
 		if (lumpnum != -1 && fileSystem.FileLength(lumpnum) != 0)
 			return true;
 	}
diff --git a/src/common/cutscenes/movieplayer.cpp b/src/common/cutscenes/movieplayer.cpp
index ecfc2d2d2..27d8f7271 100644
--- a/src/common/cutscenes/movieplayer.cpp
+++ b/src/common/cutscenes/movieplayer.cpp
@@ -508,7 +508,7 @@ public:
 			}
 			if (!MusicStream)
 			{
-				Printf(PRINT_BOLD, "Failed to decode %s\n", fileSystem.GetFileName(soundtrack, false));
+				Printf(PRINT_BOLD, "Failed to decode %s\n", fileSystem.GetFileName(soundtrack));
 			}
 		}
 		animtex.SetSize(AnimTexture::VPX, width, height);
diff --git a/src/common/engine/sc_man.cpp b/src/common/engine/sc_man.cpp
index ac7b4799f..5af08fa57 100644
--- a/src/common/engine/sc_man.cpp
+++ b/src/common/engine/sc_man.cpp
@@ -124,7 +124,7 @@ FScanner::FScanner(int lumpnum, TMap<FName, Symbol>* extsymbols) : symbols(extsy
 
 void FScanner::Open (const char *name)
 {
-	int lump = fileSystem.CheckNumForFullName(name, true);
+	int lump = fileSystem.CheckNumForAnyName(name);
 	if (lump == -1)
 	{
 		I_Error("Could not find script lump '%s'\n", name);
diff --git a/src/common/engine/serializer.cpp b/src/common/engine/serializer.cpp
index 7d947d9ce..5c5c9f566 100644
--- a/src/common/engine/serializer.cpp
+++ b/src/common/engine/serializer.cpp
@@ -58,8 +58,6 @@
 #include "vm.h"
 #include "i_interface.h"
 
-using namespace FileSys;
-
 extern DObject *WP_NOCHANGE;
 bool save_full = false;	// for testing. Should be removed afterward.
 
@@ -155,13 +153,13 @@ bool FSerializer::OpenReader(const char *buffer, size_t length)
 //
 //==========================================================================
 
-bool FSerializer::OpenReader(FCompressedBuffer *input)
+bool FSerializer::OpenReader(FileSys::FCompressedBuffer *input)
 {
 	if (input->mSize <= 0 || input->mBuffer == nullptr) return false;
 	if (w != nullptr || r != nullptr) return false;
 
 	mErrors = 0;
-	if (input->mMethod == METHOD_STORED)
+	if (input->mMethod == FileSys::METHOD_STORED)
 	{
 		r = new FReader((char*)input->mBuffer, input->mSize);
 	}
@@ -785,10 +783,10 @@ const char *FSerializer::GetOutput(unsigned *len)
 //
 //==========================================================================
 
-FCompressedBuffer FSerializer::GetCompressedOutput()
+FileSys::FCompressedBuffer FSerializer::GetCompressedOutput()
 {
 	if (isReading()) return{ 0,0,0,0,0,nullptr };
-	FCompressedBuffer buff;
+	FileSys::FCompressedBuffer buff;
 	WriteObjects();
 	EndObject();
 	buff.filename = nullptr;
@@ -827,7 +825,7 @@ FCompressedBuffer FSerializer::GetCompressedOutput()
 	if (err == Z_OK)
 	{
 		buff.mBuffer = new char[buff.mCompressedSize];
-		buff.mMethod = METHOD_DEFLATE;
+		buff.mMethod = FileSys::METHOD_DEFLATE;
 		memcpy(buff.mBuffer, compressbuf, buff.mCompressedSize);
 		delete[] compressbuf;
 		return buff;
@@ -836,7 +834,7 @@ FCompressedBuffer FSerializer::GetCompressedOutput()
 error:
 	memcpy(compressbuf, w->mOutString.GetString(), buff.mSize + 1);
 	buff.mCompressedSize = buff.mSize;
-	buff.mMethod = METHOD_STORED;
+	buff.mMethod = FileSys::METHOD_STORED;
 	return buff;
 }
 
diff --git a/src/common/engine/stringtable.cpp b/src/common/engine/stringtable.cpp
index d9d739b57..d748157db 100644
--- a/src/common/engine/stringtable.cpp
+++ b/src/common/engine/stringtable.cpp
@@ -47,7 +47,7 @@
 //
 //==========================================================================
 
-void FStringTable::LoadStrings (FileSys::FileSystem& fileSystem, const char *language)
+void FStringTable::LoadStrings (FileSystem& fileSystem, const char *language)
 {
 	int lastlump, lump;
 
diff --git a/src/common/engine/stringtable.h b/src/common/engine/stringtable.h
index 181d8c7f3..193045d9f 100644
--- a/src/common/engine/stringtable.h
+++ b/src/common/engine/stringtable.h
@@ -84,7 +84,7 @@ public:
 	using LangMap = TMap<uint32_t, StringMap>;
 	using StringMacroMap = TMap<FName, StringMacro>;
 
-	void LoadStrings(FileSys::FileSystem& fileSystem, const char *language);
+	void LoadStrings(FileSystem& fileSystem, const char *language);
 	void UpdateLanguage(const char* language);
 	StringMap GetDefaultStrings() { return allStrings[default_table]; }	// Dehacked needs these for comparison
 	void SetOverrideStrings(StringMap & map)
diff --git a/src/common/filesystem/include/fs_filesystem.h b/src/common/filesystem/include/fs_filesystem.h
index 7fc8fc50f..ce49d765f 100644
--- a/src/common/filesystem/include/fs_filesystem.h
+++ b/src/common/filesystem/include/fs_filesystem.h
@@ -66,8 +66,13 @@ public:
 	inline int GetNumForName (const uint8_t *name, int ns) const { return GetNumForName ((const char *)name, ns); }
 
 	int CheckNumForFullName (const char *cname, bool trynormal = false, int namespc = ns_global, bool ignoreext = false) const;
-	int CheckNumForFullName (const char *name, int wadfile) const;
+	int CheckNumForFullNameInFile (const char *name, int wadfile) const;
 	int GetNumForFullName (const char *name) const;
+	int CheckNumForAnyName(const char* cname, namespace_t namespc = ns_global) const
+	{
+		return CheckNumForFullName(cname, true, namespc);
+	}
+
 	int FindFile(const char* name) const
 	{
 		return CheckNumForFullName(name);
diff --git a/src/common/filesystem/include/resourcefile.h b/src/common/filesystem/include/resourcefile.h
index a23914444..e1a55ce7d 100644
--- a/src/common/filesystem/include/resourcefile.h
+++ b/src/common/filesystem/include/resourcefile.h
@@ -45,6 +45,8 @@ using FileSystemMessageFunc = int(*)(FSMessageLevel msglevel, const char* format
 
 class FResourceFile;
 
+}
+
 // [RH] Namespaces from BOOM.
 // These are needed here in the low level part so that WAD files can be properly set up.
 typedef enum {
@@ -76,6 +78,8 @@ typedef enum {
 	ns_firstskin,
 } namespace_t;
 
+namespace FileSys {
+
 enum ELumpFlags
 {
 	RESFF_MAYBEFLAT = 1,	// might be a flat inside a WAD outside F_START/END
diff --git a/src/common/filesystem/source/filesystem.cpp b/src/common/filesystem/source/filesystem.cpp
index 511686539..ec305e15f 100644
--- a/src/common/filesystem/source/filesystem.cpp
+++ b/src/common/filesystem/source/filesystem.cpp
@@ -594,7 +594,7 @@ int FileSystem::CheckNumForFullName (const char *name, bool trynormal, int names
 	return -1;
 }
 
-int FileSystem::CheckNumForFullName (const char *name, int rfnum) const
+int FileSystem::CheckNumForFullNameInFile (const char *name, int rfnum) const
 {
 	uint32_t i;
 
diff --git a/src/common/fonts/v_font.cpp b/src/common/fonts/v_font.cpp
index d838fb181..4b339d757 100644
--- a/src/common/fonts/v_font.cpp
+++ b/src/common/fonts/v_font.cpp
@@ -120,7 +120,7 @@ FFont *V_GetFont(const char *name, const char *fontlumpname)
 		}
 
 
-		lump = fileSystem.CheckNumForFullName(fontlumpname? fontlumpname : name, true);
+		lump = fileSystem.CheckNumForAnyName(fontlumpname? fontlumpname : name);
 
 		if (lump != -1 && fileSystem.GetFileContainer(lump) >= folderfile)
 		{
@@ -871,7 +871,7 @@ void V_InitFonts()
 	FFont *CreateHexLumpFont(const char *fontname, int lump);
 	FFont *CreateHexLumpFont2(const char *fontname, int lump);
 
-	auto lump = fileSystem.CheckNumForFullName("newconsolefont.hex", 0);	// This is always loaded from gzdoom.pk3 to prevent overriding it with incomplete replacements.
+	auto lump = fileSystem.CheckNumForFullNameInFile("newconsolefont.hex", 0);	// This is always loaded from gzdoom.pk3 to prevent overriding it with incomplete replacements.
 	if (lump == -1) I_FatalError("newconsolefont.hex not found");	// This font is needed - do not start up without it.
 	NewConsoleFont = CreateHexLumpFont("NewConsoleFont", lump);
 	NewSmallFont = CreateHexLumpFont2("NewSmallFont", lump);
diff --git a/src/common/menu/menudef.cpp b/src/common/menu/menudef.cpp
index ad02001e0..081263d98 100644
--- a/src/common/menu/menudef.cpp
+++ b/src/common/menu/menudef.cpp
@@ -1524,7 +1524,7 @@ void M_ParseMenuDefs()
 	DefaultOptionMenuSettings->Reset();
 	OptionSettings.mLinespacing = 17;
 
-	int IWADMenu = fileSystem.CheckNumForName("MENUDEF", FileSys::ns_global, fileSystem.GetIwadNum());
+	int IWADMenu = fileSystem.CheckNumForName("MENUDEF", ns_global, fileSystem.GetIwadNum());
 
 	while ((lump = fileSystem.FindLump ("MENUDEF", &lastlump)) != -1)
 	{
diff --git a/src/common/rendering/gl/gl_shader.cpp b/src/common/rendering/gl/gl_shader.cpp
index bafbf89b8..b091e9d1d 100644
--- a/src/common/rendering/gl/gl_shader.cpp
+++ b/src/common/rendering/gl/gl_shader.cpp
@@ -373,10 +373,10 @@ bool FShader::Load(const char * name, const char * vert_prog_lump, const char *
 	i_data += "#define NPOT_EMULATION\nuniform vec2 uNpotEmulation;\n";
 #endif
 
-	int vp_lump = fileSystem.CheckNumForFullName(vert_prog_lump, 0);
+	int vp_lump = fileSystem.CheckNumForFullNameInFile(vert_prog_lump, 0);
 	if (vp_lump == -1) I_Error("Unable to load '%s'", vert_prog_lump);
 
-	int fp_lump = fileSystem.CheckNumForFullName(frag_prog_lump, 0);
+	int fp_lump = fileSystem.CheckNumForFullNameInFile(frag_prog_lump, 0);
 	if (fp_lump == -1) I_Error("Unable to load '%s'", frag_prog_lump);
 
 
@@ -418,7 +418,7 @@ bool FShader::Load(const char * name, const char * vert_prog_lump, const char *
 
 		if (*proc_prog_lump != '#')
 		{
-			int pp_lump = fileSystem.CheckNumForFullName(proc_prog_lump, 0);	// if it's a core shader, ignore overrides by user mods.
+			int pp_lump = fileSystem.CheckNumForFullNameInFile(proc_prog_lump, 0);	// if it's a core shader, ignore overrides by user mods.
 			if (pp_lump == -1) pp_lump = fileSystem.CheckNumForFullName(proc_prog_lump);
 			if (pp_lump == -1) I_Error("Unable to load '%s'", proc_prog_lump);
 			FString pp_data = GetStringFromLump(pp_lump);
@@ -429,13 +429,13 @@ bool FShader::Load(const char * name, const char * vert_prog_lump, const char *
 
 				if (pp_data.IndexOf("GetTexCoord") >= 0)
 				{
-					int pl_lump = fileSystem.CheckNumForFullName("shaders/glsl/func_defaultmat2.fp", 0);
+					int pl_lump = fileSystem.CheckNumForFullNameInFile("shaders/glsl/func_defaultmat2.fp", 0);
 					if (pl_lump == -1) I_Error("Unable to load '%s'", "shaders/glsl/func_defaultmat2.fp");
 					fp_comb << "\n" << GetStringFromLump(pl_lump);
 				}
 				else
 				{
-					int pl_lump = fileSystem.CheckNumForFullName("shaders/glsl/func_defaultmat.fp", 0);
+					int pl_lump = fileSystem.CheckNumForFullNameInFile("shaders/glsl/func_defaultmat.fp", 0);
 					if (pl_lump == -1) I_Error("Unable to load '%s'", "shaders/glsl/func_defaultmat.fp");
 					fp_comb << "\n" << GetStringFromLump(pl_lump);
 
@@ -461,7 +461,7 @@ bool FShader::Load(const char * name, const char * vert_prog_lump, const char *
 
 			if (pp_data.IndexOf("ProcessLight") < 0)
 			{
-				int pl_lump = fileSystem.CheckNumForFullName("shaders/glsl/func_defaultlight.fp", 0);
+				int pl_lump = fileSystem.CheckNumForFullNameInFile("shaders/glsl/func_defaultlight.fp", 0);
 				if (pl_lump == -1) I_Error("Unable to load '%s'", "shaders/glsl/func_defaultlight.fp");
 				fp_comb << "\n" << GetStringFromLump(pl_lump);
 			}
@@ -483,7 +483,7 @@ bool FShader::Load(const char * name, const char * vert_prog_lump, const char *
 
 	if (light_fragprog)
 	{
-		int pp_lump = fileSystem.CheckNumForFullName(light_fragprog, 0);
+		int pp_lump = fileSystem.CheckNumForFullNameInFile(light_fragprog, 0);
 		if (pp_lump == -1) I_Error("Unable to load '%s'", light_fragprog);
 		fp_comb << GetStringFromLump(pp_lump) << "\n";
 	}
diff --git a/src/common/rendering/gles/gles_shader.cpp b/src/common/rendering/gles/gles_shader.cpp
index dba9a233a..930214a24 100644
--- a/src/common/rendering/gles/gles_shader.cpp
+++ b/src/common/rendering/gles/gles_shader.cpp
@@ -381,10 +381,10 @@ bool FShader::Load(const char * name, const char * vert_prog_lump_, const char *
 	i_data += "#define NPOT_EMULATION\nuniform vec2 uNpotEmulation;\n";
 #endif
 
-	int vp_lump = fileSystem.CheckNumForFullName(vert_prog_lump.GetChars(), 0);
+	int vp_lump = fileSystem.CheckNumForFullNameInFile(vert_prog_lump.GetChars(), 0);
 	if (vp_lump == -1) I_Error("Unable to load '%s'", vert_prog_lump.GetChars());
 
-	int fp_lump = fileSystem.CheckNumForFullName(frag_prog_lump.GetChars(), 0);
+	int fp_lump = fileSystem.CheckNumForFullNameInFile(frag_prog_lump.GetChars(), 0);
 	if (fp_lump == -1) I_Error("Unable to load '%s'", frag_prog_lump.GetChars());
 
 
@@ -428,13 +428,13 @@ bool FShader::Load(const char * name, const char * vert_prog_lump_, const char *
 
 				if (pp_data.IndexOf("GetTexCoord") >= 0)
 				{
-					int pl_lump = fileSystem.CheckNumForFullName("shaders_gles/glsl/func_defaultmat2.fp", 0);
+					int pl_lump = fileSystem.CheckNumForFullNameInFile("shaders_gles/glsl/func_defaultmat2.fp", 0);
 					if (pl_lump == -1) I_Error("Unable to load '%s'", "shaders_gles/glsl/func_defaultmat2.fp");
 					fp_comb << "\n" << GetStringFromLump(pl_lump);
 				}
 				else
 				{
-					int pl_lump = fileSystem.CheckNumForFullName("shaders_gles/glsl/func_defaultmat.fp", 0);
+					int pl_lump = fileSystem.CheckNumForFullNameInFile("shaders_gles/glsl/func_defaultmat.fp", 0);
 					if (pl_lump == -1) I_Error("Unable to load '%s'", "shaders_gles/glsl/func_defaultmat.fp");
 					fp_comb << "\n" << GetStringFromLump(pl_lump);
 
@@ -460,7 +460,7 @@ bool FShader::Load(const char * name, const char * vert_prog_lump_, const char *
 
 			if (pp_data.IndexOf("ProcessLight") < 0)
 			{
-				int pl_lump = fileSystem.CheckNumForFullName("shaders_gles/glsl/func_defaultlight.fp", 0);
+				int pl_lump = fileSystem.CheckNumForFullNameInFile("shaders_gles/glsl/func_defaultlight.fp", 0);
 				if (pl_lump == -1) I_Error("Unable to load '%s'", "shaders_gles/glsl/func_defaultlight.fp");
 				fp_comb << "\n" << GetStringFromLump(pl_lump);
 			}
@@ -482,7 +482,7 @@ bool FShader::Load(const char * name, const char * vert_prog_lump_, const char *
 
 	if (light_fragprog.Len())
 	{
-		int pp_lump = fileSystem.CheckNumForFullName(light_fragprog.GetChars(), 0);
+		int pp_lump = fileSystem.CheckNumForFullNameInFile(light_fragprog.GetChars(), 0);
 		if (pp_lump == -1) I_Error("Unable to load '%s'", light_fragprog.GetChars());
 		fp_comb << GetStringFromLump(pp_lump) << "\n";
 	}
diff --git a/src/common/rendering/vulkan/shaders/vk_shader.cpp b/src/common/rendering/vulkan/shaders/vk_shader.cpp
index 00734ac7f..a04fb972c 100644
--- a/src/common/rendering/vulkan/shaders/vk_shader.cpp
+++ b/src/common/rendering/vulkan/shaders/vk_shader.cpp
@@ -465,7 +465,7 @@ FString VkShaderManager::GetTargetGlslVersion()
 
 FString VkShaderManager::LoadPublicShaderLump(const char *lumpname)
 {
-	int lump = fileSystem.CheckNumForFullName(lumpname, 0);
+	int lump = fileSystem.CheckNumForFullNameInFile(lumpname, 0);
 	if (lump == -1) lump = fileSystem.CheckNumForFullName(lumpname);
 	if (lump == -1) I_Error("Unable to load '%s'", lumpname);
 	return GetStringFromLump(lump);
@@ -473,7 +473,7 @@ FString VkShaderManager::LoadPublicShaderLump(const char *lumpname)
 
 FString VkShaderManager::LoadPrivateShaderLump(const char *lumpname)
 {
-	int lump = fileSystem.CheckNumForFullName(lumpname, 0);
+	int lump = fileSystem.CheckNumForFullNameInFile(lumpname, 0);
 	if (lump == -1) I_Error("Unable to load '%s'", lumpname);
 	return GetStringFromLump(lump);
 }
diff --git a/src/common/scripting/frontend/zcc_parser.cpp b/src/common/scripting/frontend/zcc_parser.cpp
index 6ea3c316e..e96ccc773 100644
--- a/src/common/scripting/frontend/zcc_parser.cpp
+++ b/src/common/scripting/frontend/zcc_parser.cpp
@@ -304,7 +304,7 @@ static void ParseSingleFile(FScanner *pSC, const char *filename, int lump, void
 	{
 		if (filename != nullptr)
 		{
-			lump = fileSystem.CheckNumForFullName(filename, true);
+			lump = fileSystem.CheckNumForAnyName(filename);
 			if (lump >= 0)
 			{
 				lsc.OpenLumpNum(lump);
@@ -480,7 +480,7 @@ PNamespace *ParseOneScript(const int baselump, ZCCParseState &state)
 	ParseSingleFile(&sc, nullptr, lumpnum, parser, state);
 	for (unsigned i = 0; i < Includes.Size(); i++)
 	{
-		lumpnum = fileSystem.CheckNumForFullName(Includes[i].GetChars(), true);
+		lumpnum = fileSystem.CheckNumForAnyName(Includes[i].GetChars());
 		if (lumpnum == -1)
 		{
 			IncludeLocs[i].Message(MSG_ERROR, "Include script lump %s not found", Includes[i].GetChars());
diff --git a/src/common/startscreen/endoom.cpp b/src/common/startscreen/endoom.cpp
index 6e8e7af35..4dd160c0f 100644
--- a/src/common/startscreen/endoom.cpp
+++ b/src/common/startscreen/endoom.cpp
@@ -153,7 +153,7 @@ int RunEndoom()
 		return 0;
 	}
 
-	int endoom_lump = fileSystem.CheckNumForFullName (endoomName.GetChars(), true);
+	int endoom_lump = fileSystem.CheckNumForAnyName (endoomName.GetChars());
 	
 	if (endoom_lump < 0 || fileSystem.FileLength (endoom_lump) != 4000)
 	{
diff --git a/src/common/startscreen/startscreen_generic.cpp b/src/common/startscreen/startscreen_generic.cpp
index b76cbd3e2..4c41bc7a8 100644
--- a/src/common/startscreen/startscreen_generic.cpp
+++ b/src/common/startscreen/startscreen_generic.cpp
@@ -72,7 +72,7 @@ FGenericStartScreen::FGenericStartScreen(int max_progress)
 	: FStartScreen(max_progress)
 {
 	// at this point we do not have a working texture manager yet, so we have to do the lookup via the file system
-	int startup_lump = fileSystem.CheckNumForName("BOOTLOGO", FileSys::ns_graphics);
+	int startup_lump = fileSystem.CheckNumForName("BOOTLOGO", ns_graphics);
 
 	StartupBitmap.Create(640 * 2, 480 * 2);
 	ClearBlock(StartupBitmap, { 0, 0, 0, 255 }, 0, 0, 640 * 2, 480 * 2);
diff --git a/src/common/startscreen/startscreen_hexen.cpp b/src/common/startscreen/startscreen_hexen.cpp
index a82e21b35..6eef73599 100644
--- a/src/common/startscreen/startscreen_hexen.cpp
+++ b/src/common/startscreen/startscreen_hexen.cpp
@@ -81,9 +81,9 @@ FHexenStartScreen::FHexenStartScreen(int max_progress)
 	: FStartScreen(max_progress)
 {
 	// at this point we do not have a working texture manager yet, so we have to do the lookup via the file system
-	int startup_lump = fileSystem.CheckNumForName("STARTUP", FileSys::ns_graphics);
-	int netnotch_lump = fileSystem.CheckNumForName("NETNOTCH", FileSys::ns_graphics);
-	int notch_lump = fileSystem.CheckNumForName("NOTCH", FileSys::ns_graphics);
+	int startup_lump = fileSystem.CheckNumForName("STARTUP", ns_graphics);
+	int netnotch_lump = fileSystem.CheckNumForName("NETNOTCH", ns_graphics);
+	int notch_lump = fileSystem.CheckNumForName("NOTCH", ns_graphics);
 
 	// For backwards compatibility we also need to look in the default namespace, because these were previously not handled as graphics.
 	if (startup_lump == -1) startup_lump = fileSystem.CheckNumForName("STARTUP");
diff --git a/src/common/startscreen/startscreen_strife.cpp b/src/common/startscreen/startscreen_strife.cpp
index df5467f96..8f02b2022 100644
--- a/src/common/startscreen/startscreen_strife.cpp
+++ b/src/common/startscreen/startscreen_strife.cpp
@@ -111,7 +111,7 @@ FStrifeStartScreen::FStrifeStartScreen(int max_progress)
 	// Load the background and animated overlays.
 	for (size_t i = 0; i < countof(StrifeStartupPicNames); ++i)
 	{
-		int lumpnum = fileSystem.CheckNumForName(StrifeStartupPicNames[i], FileSys::ns_graphics);
+		int lumpnum = fileSystem.CheckNumForName(StrifeStartupPicNames[i], ns_graphics);
 		if (lumpnum < 0) lumpnum = fileSystem.CheckNumForName(StrifeStartupPicNames[i]);
 
 		if (lumpnum >= 0)
diff --git a/src/common/textures/gametexture.cpp b/src/common/textures/gametexture.cpp
index 179ea5a8f..28acc5c24 100644
--- a/src/common/textures/gametexture.cpp
+++ b/src/common/textures/gametexture.cpp
@@ -182,7 +182,7 @@ void FGameTexture::AddAutoMaterials()
 		if (this->*(layer.pointer) == nullptr)	// only if no explicit assignment had been done.
 		{
 			FStringf lookup("%s%s%s", layer.path, fullname ? "" : "auto/", searchname.GetChars());
-			auto lump = fileSystem.CheckNumForFullName(lookup.GetChars(), false, FileSys::ns_global, true);
+			auto lump = fileSystem.CheckNumForFullName(lookup.GetChars(), true);
 			if (lump != -1)
 			{
 				auto bmtex = TexMan.FindGameTexture(fileSystem.GetFileName(lump), ETextureType::Any, FTextureManager::TEXMAN_TryAny);
@@ -199,7 +199,7 @@ void FGameTexture::AddAutoMaterials()
 		if (!this->Layers || this->Layers.get()->*(layer.pointer) == nullptr)	// only if no explicit assignment had been done.
 		{
 			FStringf lookup("%s%s%s", layer.path, fullname ? "" : "auto/", searchname.GetChars());
-			auto lump = fileSystem.CheckNumForFullName(lookup.GetChars(), false, FileSys::ns_global, true);
+			auto lump = fileSystem.CheckNumForFullName(lookup.GetChars(), true);
 			if (lump != -1)
 			{
 				auto bmtex = TexMan.FindGameTexture(fileSystem.GetFileName(lump), ETextureType::Any, FTextureManager::TEXMAN_TryAny);
diff --git a/src/common/textures/texturemanager.cpp b/src/common/textures/texturemanager.cpp
index 63b2adee7..a84639a8c 100644
--- a/src/common/textures/texturemanager.cpp
+++ b/src/common/textures/texturemanager.cpp
@@ -723,8 +723,8 @@ void FTextureManager::ParseTextureDef(int lump, FMultipatchTextureBuilder &build
 			FName texname = sc.String;
 
 			sc.MustGetString();
-			int lumpnum = fileSystem.CheckNumForFullName(sc.String, true, ns_patches);
-			if (lumpnum == -1) lumpnum = fileSystem.CheckNumForFullName(sc.String, true, ns_graphics);
+			int lumpnum = fileSystem.CheckNumForAnyName(sc.String, ns_patches);
+			if (lumpnum == -1) lumpnum = fileSystem.CheckNumForAnyName(sc.String, ns_graphics);
 
 			if (tlist.Size() == 0)
 			{
@@ -779,8 +779,8 @@ void FTextureManager::ParseTextureDef(int lump, FMultipatchTextureBuilder &build
 			{
 				FString src = base.Left(8);
 
-				int lumpnum = fileSystem.CheckNumForFullName(sc.String, true, ns_patches);
-				if (lumpnum == -1) lumpnum = fileSystem.CheckNumForFullName(sc.String, true, ns_graphics);
+				int lumpnum = fileSystem.CheckNumForAnyName(sc.String, ns_patches);
+				if (lumpnum == -1) lumpnum = fileSystem.CheckNumForAnyName(sc.String, ns_graphics);
 
 				sc.GetString();
 				bool is32bit = !!sc.Compare("force32bit");
@@ -854,7 +854,7 @@ void FTextureManager::ParseTextureDef(int lump, FMultipatchTextureBuilder &build
 			sc.MustGetString();
 
 			// This is not using sc.Open because it can print a more useful error message when done here
-			int includelump = fileSystem.CheckNumForFullName(sc.String, true);
+			int includelump = fileSystem.CheckNumForAnyName(sc.String);
 			if (includelump == -1)
 			{
 				sc.ScriptError("Lump '%s' not found", sc.String);
@@ -971,7 +971,7 @@ void FTextureManager::AddTexturesForWad(int wadnum, FMultipatchTextureBuilder &b
 		if (ns == ns_global)
 		{
 			// In Zips all graphics must be in a separate namespace.
-			if (fileSystem.GetFileFlags(i) & RESFF_FULLPATH) continue;
+			if (fileSystem.GetFileFlags(i) & FileSys::RESFF_FULLPATH) continue;
 
 			// Ignore lumps with empty names.
 			if (fileSystem.CheckFileName(i, "")) continue;
@@ -1109,7 +1109,7 @@ void FTextureManager::SortTexturesByType(int start, int end)
 
 void FTextureManager::AddLocalizedVariants()
 {
-	std::vector<FolderEntry> content;
+	std::vector<FileSys::FolderEntry> content;
 	fileSystem.GetFilesInFolder("localized/textures/", content, false);
 	for (auto &entry : content)
 	{
diff --git a/src/d_main.cpp b/src/d_main.cpp
index 9c1c6931f..aa5bfdf9a 100644
--- a/src/d_main.cpp
+++ b/src/d_main.cpp
@@ -1984,8 +1984,8 @@ static FString CheckGameInfo(std::vector<std::string> & pwads)
 static void SetMapxxFlag()
 {
 	int lump_name = fileSystem.CheckNumForName("MAP01", ns_global, fileSystem.GetIwadNum());
-	int lump_wad = fileSystem.CheckNumForFullName("maps/map01.wad", fileSystem.GetIwadNum());
-	int lump_map = fileSystem.CheckNumForFullName("maps/map01.map", fileSystem.GetIwadNum());
+	int lump_wad = fileSystem.CheckNumForFullNameInFile("maps/map01.wad", fileSystem.GetIwadNum());
+	int lump_map = fileSystem.CheckNumForFullNameInFile("maps/map01.map", fileSystem.GetIwadNum());
 
 	if (lump_name >= 0 || lump_wad >= 0 || lump_map >= 0) gameinfo.flags |= GI_MAPxx;
 }
diff --git a/src/g_game.cpp b/src/g_game.cpp
index f43642813..7c7161aef 100644
--- a/src/g_game.cpp
+++ b/src/g_game.cpp
@@ -2909,7 +2909,7 @@ void G_DoPlayDemo (void)
 	gameaction = ga_nothing;
 
 	// [RH] Allow for demos not loaded as lumps
-	demolump = fileSystem.CheckNumForFullName (defdemoname.GetChars(), true);
+	demolump = fileSystem.CheckNumForAnyName (defdemoname.GetChars());
 	if (demolump >= 0)
 	{
 		int demolen = fileSystem.FileLength (demolump);
diff --git a/src/g_statusbar/sbarinfo.cpp b/src/g_statusbar/sbarinfo.cpp
index 6bb27d179..70351664d 100644
--- a/src/g_statusbar/sbarinfo.cpp
+++ b/src/g_statusbar/sbarinfo.cpp
@@ -443,7 +443,7 @@ void SBarInfo::Load()
 {
 	if(gameinfo.statusbar.IsNotEmpty())
 	{
-		int lump = fileSystem.CheckNumForFullName(gameinfo.statusbar.GetChars(), true);
+		int lump = fileSystem.CheckNumForAnyName(gameinfo.statusbar.GetChars());
 		if(lump != -1)
 		{
 			if (!batchrun) Printf ("ParseSBarInfo: Loading default status bar definition.\n");
@@ -481,7 +481,7 @@ void SBarInfo::ParseSBarInfo(int lump)
 		if(sc.TokenType == TK_Include)
 		{
 			sc.MustGetToken(TK_StringConst);
-			int lump = fileSystem.CheckNumForFullName(sc.String, true);
+			int lump = fileSystem.CheckNumForAnyName(sc.String);
 			if (lump == -1)
 				sc.ScriptError("Lump '%s' not found", sc.String);
 			ParseSBarInfo(lump);
@@ -496,15 +496,15 @@ void SBarInfo::ParseSBarInfo(int lump)
 					sc.MustGetToken(TK_Identifier);
 				if(sc.Compare("Doom"))
 				{
-					baselump = fileSystem.CheckNumForFullName("sbarinfo/doom.txt", true);
+					baselump = fileSystem.CheckNumForFullName("sbarinfo/doom.txt");
 				}
 				else if(sc.Compare("Heretic"))
 				{
-					baselump = fileSystem.CheckNumForFullName("sbarinfo/heretic.txt", true);
+					baselump = fileSystem.CheckNumForFullName("sbarinfo/heretic.txt");
 				}
 				else if(sc.Compare("Hexen"))
 				{
-					baselump = fileSystem.CheckNumForFullName("sbarinfo/hexen.txt", true);
+					baselump = fileSystem.CheckNumForFullName("sbarinfo/hexen.txt");
 				}
 				else if(sc.Compare("Strife"))
 					gameType = GAME_Strife;
diff --git a/src/gamedata/d_dehacked.cpp b/src/gamedata/d_dehacked.cpp
index cc9412f17..717ffcd0b 100644
--- a/src/gamedata/d_dehacked.cpp
+++ b/src/gamedata/d_dehacked.cpp
@@ -168,7 +168,7 @@ static void ReplaceSoundName(int index, const char* newname)
 	if (snd == NO_SOUND) return;
 	auto sfx = soundEngine->GetWritableSfx(snd);
 	FStringf dsname("ds%s", newname);
-	sfx->lumpnum = fileSystem.CheckNumForName(dsname.GetChars(), FileSys::ns_sounds);
+	sfx->lumpnum = fileSystem.CheckNumForName(dsname.GetChars(), ns_sounds);
 	sfx->bTentative = false;
 	sfx->bRandomHeader = false;
 	sfx->bLoadRAW = false;
@@ -3205,7 +3205,7 @@ bool D_LoadDehFile(const char *patchfile, int flags)
 	else
 	{
 		// Couldn't find it in the filesystem; try from a lump instead.
-		int lumpnum = fileSystem.CheckNumForFullName(patchfile, true);
+		int lumpnum = fileSystem.CheckNumForFullName(patchfile);
 		if (lumpnum < 0)
 		{
 			// Compatibility fallback. It's just here because
diff --git a/src/gamedata/decallib.cpp b/src/gamedata/decallib.cpp
index 0f6e656b5..2d3888a2f 100644
--- a/src/gamedata/decallib.cpp
+++ b/src/gamedata/decallib.cpp
@@ -397,7 +397,7 @@ void FDecalLib::ParseDecal (FScanner &sc)
 		case DECAL_PIC:
 			sc.MustGetString ();
 			picnum = TexMan.CheckForTexture (sc.String, ETextureType::Any);
-			if (!picnum.Exists() && (lumpnum = fileSystem.CheckNumForName (sc.String, FileSys::ns_graphics)) >= 0)
+			if (!picnum.Exists() && (lumpnum = fileSystem.CheckNumForName (sc.String, ns_graphics)) >= 0)
 			{
 				picnum = TexMan.CreateTexture (lumpnum, ETextureType::Decal);
 			}
diff --git a/src/gamedata/doomfont.h b/src/gamedata/doomfont.h
index fedeb513c..b9d14db7d 100644
--- a/src/gamedata/doomfont.h
+++ b/src/gamedata/doomfont.h
@@ -18,7 +18,7 @@ void InitDoomFonts()
 		if (fileSystem.CheckNumForName("FONTA_S") >= 0)
 		{
 			int wadfile = -1;
-			auto a = fileSystem.CheckNumForName("FONTA33", FileSys::ns_graphics);
+			auto a = fileSystem.CheckNumForName("FONTA33", ns_graphics);
 			if (a != -1) wadfile = fileSystem.GetFileContainer(a);
 			if (wadfile > fileSystem.GetIwadNum())
 			{
@@ -32,10 +32,10 @@ void InitDoomFonts()
 				SmallFont->SetCursor('[');
 			}
 		}
-		else if (fileSystem.CheckNumForName("STCFN033", FileSys::ns_graphics) >= 0)
+		else if (fileSystem.CheckNumForName("STCFN033", ns_graphics) >= 0)
 		{
 			int wadfile = -1;
-			auto a = fileSystem.CheckNumForName("STCFN065", FileSys::ns_graphics);
+			auto a = fileSystem.CheckNumForName("STCFN065", ns_graphics);
 			if (a != -1) wadfile = fileSystem.GetFileContainer(a);
 			if (wadfile > fileSystem.GetIwadNum())
 			{
@@ -55,7 +55,7 @@ void InitDoomFonts()
 		OriginalSmallFont = new FFont("OriginalSmallFont", "FONTA%02u", "defsmallfont", HU_FONTSTART, HU_FONTSIZE, 1, -1, -1, false, true);
 		OriginalSmallFont->SetCursor('[');
 	}
-	else if (fileSystem.CheckNumForName("STCFN033", FileSys::ns_graphics) >= 0)
+	else if (fileSystem.CheckNumForName("STCFN033", ns_graphics) >= 0)
 	{
 		OriginalSmallFont = new FFont("OriginalSmallFont", "STCFN%.3d", "defsmallfont", HU_FONTSTART, HU_FONTSIZE, HU_FONTSTART, -1, -1, false, true, true);
 	}
@@ -63,7 +63,7 @@ void InitDoomFonts()
 
 	if (!(SmallFont2 = V_GetFont("SmallFont2")))	// Only used by Strife
 	{
-		if (fileSystem.CheckNumForName("STBFN033", FileSys::ns_graphics) >= 0)
+		if (fileSystem.CheckNumForName("STBFN033", ns_graphics) >= 0)
 		{
 			SmallFont2 = new FFont("SmallFont2", "STBFN%.3d", "defsmallfont2", HU_FONTSTART, HU_FONTSIZE, HU_FONTSTART, -1);
 		}
diff --git a/src/gamedata/g_mapinfo.cpp b/src/gamedata/g_mapinfo.cpp
index 22981062b..dcd5fd7ee 100644
--- a/src/gamedata/g_mapinfo.cpp
+++ b/src/gamedata/g_mapinfo.cpp
@@ -941,7 +941,7 @@ void FMapInfoParser::ParseCluster()
 	// Remap Hexen's CLUS?MSG lumps to the string table, if applicable. The code here only checks what can actually be in an IWAD.
 	if (clusterinfo->flags & CLUSTER_EXITTEXTINLUMP)
 	{
-		int lump = fileSystem.CheckNumForFullName(clusterinfo->ExitText.GetChars(), true);
+		int lump = fileSystem.CheckNumForAnyName(clusterinfo->ExitText.GetChars());
 		if (lump > 0)
 		{
 			// Check if this comes from either Hexen.wad or Hexdd.wad and if so, map to the string table.
@@ -2447,7 +2447,7 @@ void FMapInfoParser::ParseMapInfo (int lump, level_info_t &gamedefaults, level_i
 		if (sc.Compare("include"))
 		{
 			sc.MustGetString();
-			int inclump = fileSystem.CheckNumForFullName(sc.String, true);
+			int inclump = fileSystem.CheckNumForAnyName(sc.String);
 			if (inclump < 0)
 			{
 				sc.ScriptError("include file '%s' not found", sc.String);
@@ -2725,7 +2725,7 @@ void G_ParseMapInfo (FString basemapinfo)
 			// If that exists we need to skip this one.
 
 			int wad = fileSystem.GetFileContainer(lump);
-			int altlump = fileSystem.CheckNumForName("ZMAPINFO", FileSys::ns_global, wad, true);
+			int altlump = fileSystem.CheckNumForName("ZMAPINFO", ns_global, wad, true);
 
 			if (altlump >= 0) continue;
 		}
@@ -2733,9 +2733,9 @@ void G_ParseMapInfo (FString basemapinfo)
 		{
 			// MAPINFO and ZMAPINFO will override UMAPINFO if in the same WAD.
 			int wad = fileSystem.GetFileContainer(lump);
-			int altlump = fileSystem.CheckNumForName("ZMAPINFO", FileSys::ns_global, wad, true);
+			int altlump = fileSystem.CheckNumForName("ZMAPINFO", ns_global, wad, true);
 			if (altlump >= 0) continue;
-			altlump = fileSystem.CheckNumForName("MAPINFO", FileSys::ns_global, wad, true);
+			altlump = fileSystem.CheckNumForName("MAPINFO", ns_global, wad, true);
 			if (altlump >= 0) continue;
 		}
 		if (nindex != 2)
diff --git a/src/gamedata/textures/buildloader.cpp b/src/gamedata/textures/buildloader.cpp
index d31d18ce4..ca55a8954 100644
--- a/src/gamedata/textures/buildloader.cpp
+++ b/src/gamedata/textures/buildloader.cpp
@@ -276,7 +276,7 @@ void InitBuildTiles()
 				// only read from the same source as the palette.
 				// The entire format here is just too volatile to allow liberal mixing.
 				// An .ART set must be treated as one unit.
-				lumpnum = fileSystem.CheckNumForFullName(artpath.GetChars(), fileSystem.GetFileContainer(i));
+				lumpnum = fileSystem.CheckNumForFullNameInFile(artpath.GetChars(), fileSystem.GetFileContainer(i));
 				if (lumpnum < 0)
 				{
 					break;
diff --git a/src/gamedata/xlat/parsecontext.cpp b/src/gamedata/xlat/parsecontext.cpp
index 0caa72f4b..1f0563aac 100644
--- a/src/gamedata/xlat/parsecontext.cpp
+++ b/src/gamedata/xlat/parsecontext.cpp
@@ -314,7 +314,7 @@ void FParseContext::ParseLump(const char *lumpname)
 	const char *SavedSourceFile = SourceFile;
 	FParseToken token;
 
-	int lumpno = fileSystem.CheckNumForFullName(lumpname, true);
+	int lumpno = fileSystem.CheckNumForAnyName(lumpname);
 
 	if (lumpno == -1) 
 	{
diff --git a/src/intermission/intermission_parse.cpp b/src/intermission/intermission_parse.cpp
index d1089526b..c2c07dc31 100644
--- a/src/intermission/intermission_parse.cpp
+++ b/src/intermission/intermission_parse.cpp
@@ -303,7 +303,7 @@ bool FIntermissionActionTextscreen::ParseKey(FScanner &sc)
 	{
 		sc.MustGetToken('=');
 		sc.MustGetToken(TK_StringConst);
-		int lump = fileSystem.CheckNumForFullName(sc.String, true);
+		int lump = fileSystem.CheckNumForAnyName(sc.String);
 		bool done = false;
 		if (lump > 0)
 		{
@@ -861,7 +861,7 @@ DIntermissionController* F_StartFinale (const char *music, int musicorder, int c
 		FIntermissionActionTextscreen *textscreen = new FIntermissionActionTextscreen;
 		if (textInLump)
 		{
-			int lump = fileSystem.CheckNumForFullName(text, true);
+			int lump = fileSystem.CheckNumForAnyName(text);
 			if (lump > 0)
 			{
 				textscreen->mText = GetStringFromLump(lump);
diff --git a/src/maploader/edata.cpp b/src/maploader/edata.cpp
index 044fb0811..3e89b7dfa 100644
--- a/src/maploader/edata.cpp
+++ b/src/maploader/edata.cpp
@@ -520,7 +520,7 @@ void MapLoader::InitED()
 	FScanner sc;
 
 	if (filename.IsEmpty()) return;
-	int lump = fileSystem.CheckNumForFullName(filename.GetChars(), true, FileSys::ns_global);
+	int lump = fileSystem.CheckNumForAnyName(filename.GetChars(), ns_global);
 	if (lump == -1) return;
 	sc.OpenLumpNum(lump);
 
diff --git a/src/maploader/glnodes.cpp b/src/maploader/glnodes.cpp
index 4768b838e..d61f95f8a 100644
--- a/src/maploader/glnodes.cpp
+++ b/src/maploader/glnodes.cpp
@@ -730,14 +730,14 @@ static int FindGLNodesInWAD(int labellump)
 	glheader.Format("GL_%s", fileSystem.GetFileName(labellump));
 	if (glheader.Len()<=8)
 	{
-		int gllabel = fileSystem.CheckNumForName(glheader.GetChars(), FileSys::ns_global, wadfile);
+		int gllabel = fileSystem.CheckNumForName(glheader.GetChars(), ns_global, wadfile);
 		if (gllabel >= 0) return gllabel;
 	}
 	else
 	{
 		// Before scanning the entire WAD directory let's check first whether
 		// it is necessary.
-		int gllabel = fileSystem.CheckNumForName("GL_LEVEL", FileSys::ns_global, wadfile);
+		int gllabel = fileSystem.CheckNumForName("GL_LEVEL", ns_global, wadfile);
 
 		if (gllabel >= 0)
 		{
diff --git a/src/playsim/fragglescript/t_func.cpp b/src/playsim/fragglescript/t_func.cpp
index f9fff1b9e..b543a4447 100644
--- a/src/playsim/fragglescript/t_func.cpp
+++ b/src/playsim/fragglescript/t_func.cpp
@@ -54,8 +54,6 @@
 #include "s_music.h"
 #include "texturemanager.h"
 
-using namespace FileSys;
-
 static FRandom pr_script("FScript");
 
 // functions. FParser::SF_ means Script Function not, well.. heh, me
diff --git a/src/playsim/p_acs.cpp b/src/playsim/p_acs.cpp
index d99663bde..95b1f5d37 100644
--- a/src/playsim/p_acs.cpp
+++ b/src/playsim/p_acs.cpp
@@ -1930,7 +1930,7 @@ void FBehaviorContainer::LoadDefaultModules ()
 		FScanner sc(lump);
 		while (sc.GetString())
 		{
-			int acslump = fileSystem.CheckNumForName (sc.String, FileSys::ns_acslibrary);
+			int acslump = fileSystem.CheckNumForName (sc.String, ns_acslibrary);
 			if (acslump >= 0)
 			{
 				LoadModule (acslump);
@@ -2567,7 +2567,7 @@ bool FBehavior::Init(FLevelLocals *Level, int lumpnum, FileReader * fr, int len,
 				if (parse[i])
 				{
 					FBehavior *module = NULL;
-					int lump = fileSystem.CheckNumForName (&parse[i], FileSys::ns_acslibrary);
+					int lump = fileSystem.CheckNumForName (&parse[i], ns_acslibrary);
 					if (lump < 0)
 					{
 						Printf (TEXTCOLOR_RED "Could not find ACS library %s.\n", &parse[i]);
diff --git a/src/playsim/p_user.cpp b/src/playsim/p_user.cpp
index 652d533ca..791dd847b 100644
--- a/src/playsim/p_user.cpp
+++ b/src/playsim/p_user.cpp
@@ -874,16 +874,16 @@ static int SetupCrouchSprite(AActor *self, int crouchsprite)
 		FString normspritename = sprites[self->SpawnState->sprite].name;
 		FString crouchspritename = sprites[crouchsprite].name;
 
-		int spritenorm = fileSystem.CheckNumForName((normspritename + "A1").GetChars(), FileSys::ns_sprites);
+		int spritenorm = fileSystem.CheckNumForName((normspritename + "A1").GetChars(), ns_sprites);
 		if (spritenorm == -1)
 		{
-			spritenorm = fileSystem.CheckNumForName((normspritename + "A0").GetChars(), FileSys::ns_sprites);
+			spritenorm = fileSystem.CheckNumForName((normspritename + "A0").GetChars(), ns_sprites);
 		}
 
-		int spritecrouch = fileSystem.CheckNumForName((crouchspritename + "A1").GetChars(), FileSys::ns_sprites);
+		int spritecrouch = fileSystem.CheckNumForName((crouchspritename + "A1").GetChars(), ns_sprites);
 		if (spritecrouch == -1)
 		{
-			spritecrouch = fileSystem.CheckNumForName((crouchspritename + "A0").GetChars(), FileSys::ns_sprites);
+			spritecrouch = fileSystem.CheckNumForName((crouchspritename + "A0").GetChars(), ns_sprites);
 		}
 
 		if (spritenorm == -1 || spritecrouch == -1)
diff --git a/src/r_data/colormaps.cpp b/src/r_data/colormaps.cpp
index 4d9604b61..ad1559c6b 100644
--- a/src/r_data/colormaps.cpp
+++ b/src/r_data/colormaps.cpp
@@ -104,11 +104,11 @@ void R_InitColormaps (bool allowCustomColormap)
 
 	for (uint32_t i = 0; i < NumLumps; i++)
 	{
-		if (fileSystem.GetFileNamespace(i) == FileSys::ns_colormaps)
+		if (fileSystem.GetFileNamespace(i) == ns_colormaps)
 		{
 			auto name = fileSystem.GetFileShortName(i);
 
-			if (fileSystem.CheckNumForName (name, FileSys::ns_colormaps) == (int)i)
+			if (fileSystem.CheckNumForName (name, ns_colormaps) == (int)i)
 			{
 				strncpy(cm.name, name, 8);
 				cm.blend = 0;
diff --git a/src/r_data/gldefs.cpp b/src/r_data/gldefs.cpp
index d92b9daf6..29774d3d1 100644
--- a/src/r_data/gldefs.cpp
+++ b/src/r_data/gldefs.cpp
@@ -134,7 +134,7 @@ static void ParseVavoomSkybox()
 				sc.MustGetStringName("map");
 				sc.MustGetString();
 
-				maplump = fileSystem.CheckNumForFullName(sc.String, true);
+				maplump = fileSystem.CheckNumForAnyName(sc.String);
 
 				auto tex = TexMan.FindGameTexture(sc.String, ETextureType::Wall, FTextureManager::TEXMAN_TryAny);
 				if (tex == NULL)
@@ -1928,7 +1928,7 @@ public:
 				{
 					sc.MustGetString();
 					// This is not using sc.Open because it can print a more useful error message when done here
-					lump = fileSystem.CheckNumForFullName(sc.String, true);
+					lump = fileSystem.CheckNumForAnyName(sc.String);
 					if (lump==-1)
 						sc.ScriptError("Lump '%s' not found", sc.String);
 
diff --git a/src/r_data/models.cpp b/src/r_data/models.cpp
index a13d56998..0028966e0 100644
--- a/src/r_data/models.cpp
+++ b/src/r_data/models.cpp
@@ -1050,7 +1050,7 @@ void ParseModelDefLump(int Lump)
 		{
 			sc.MustGetString();
 			// This is not using sc.Open because it can print a more useful error message when done here
-			int includelump = fileSystem.CheckNumForFullName(sc.String, true);
+			int includelump = fileSystem.CheckNumForAnyName(sc.String);
 			if (includelump == -1)
 			{
 				if (strcmp(sc.String, "sentinel.modl") != 0) // Gene Tech mod has a broken #include statement
diff --git a/src/r_data/r_translate.cpp b/src/r_data/r_translate.cpp
index 8b197cda7..93bb023b8 100644
--- a/src/r_data/r_translate.cpp
+++ b/src/r_data/r_translate.cpp
@@ -783,7 +783,7 @@ void R_ParseTrnslate()
 			do
 			{
 				sc.MustGetToken(TK_StringConst);
-				int pallump = fileSystem.CheckNumForFullName(sc.String, true, FileSys::ns_global);
+				int pallump = fileSystem.CheckNumForAnyName(sc.String, ns_global);
 				if (pallump >= 0)	// 
 				{
 					int start = 0;
diff --git a/src/r_data/sprites.cpp b/src/r_data/sprites.cpp
index 0a7be96a1..963992321 100644
--- a/src/r_data/sprites.cpp
+++ b/src/r_data/sprites.cpp
@@ -349,7 +349,7 @@ void R_InitSpriteDefs ()
 	memset(vhashes.Data(), -1, sizeof(VHasher)*vmax);
 	for (i = 0; i < vmax; ++i)
 	{
-		if (fileSystem.GetFileNamespace(i) == FileSys::ns_voxels)
+		if (fileSystem.GetFileNamespace(i) == ns_voxels)
 		{
 			size_t namelen;
 			int spin;
@@ -715,7 +715,7 @@ void R_InitSkins (void)
 				int lump = fileSystem.CheckNumForName (sc.String, Skins[i].namespc);
 				if (lump == -1)
 				{
-					lump = fileSystem.CheckNumForFullName (sc.String, true, FileSys::ns_sounds);
+					lump = fileSystem.CheckNumForAnyName (sc.String, ns_sounds);
 				}
 				if (lump != -1)
 				{
@@ -748,7 +748,7 @@ void R_InitSkins (void)
 						sndlumps[j] = fileSystem.CheckNumForName (sc.String, Skins[i].namespc);
 						if (sndlumps[j] == -1)
 						{ // Replacement not found, try finding it in the global namespace
-							sndlumps[j] = fileSystem.CheckNumForFullName (sc.String, true, FileSys::ns_sounds);
+							sndlumps[j] = fileSystem.CheckNumForAnyName (sc.String, ns_sounds);
 						}
 					}
 				}
@@ -946,7 +946,7 @@ CCMD (skins)
 
 static void R_CreateSkinTranslation (const char *palname)
 {
-	auto lump =  fileSystem.ReadFile (palname);
+	auto lump =  fileSystem.ReadFile (fileSystem.GetNumForName(palname));
 	auto otherPal = lump.bytes();
  
 	for (int i = 0; i < 256; ++i)
@@ -1016,7 +1016,7 @@ void R_InitSprites ()
 		Skins[i].range0end = basetype->IntVar(NAME_ColorRangeEnd);
 		Skins[i].Scale = basetype->Scale;
 		Skins[i].sprite = basetype->SpawnState->sprite;
-		Skins[i].namespc = FileSys::ns_global;
+		Skins[i].namespc = ns_global;
 
 		PlayerClasses[i].Skins.Push (i);
 
diff --git a/src/r_data/v_palette.cpp b/src/r_data/v_palette.cpp
index 8af454445..977206c78 100644
--- a/src/r_data/v_palette.cpp
+++ b/src/r_data/v_palette.cpp
@@ -44,8 +44,6 @@
 #include "m_png.h"
 #include "v_colortables.h"
 
-using namespace FileSys;
-
 /* Current color blending values */
 int		BlendR, BlendG, BlendB, BlendA;
 
@@ -64,7 +62,7 @@ void InitPalette ()
 	if (lump == -1) lump = fileSystem.CheckNumForName("COLORMAP", ns_colormaps);
 	if (lump != -1)
 	{
-		FileData cmap = fileSystem.ReadFile(lump);
+		auto cmap = fileSystem.ReadFile(lump);
 		auto cmapdata = cmap.bytes();
 		GPalette.GenerateGlobalBrightmapFromColormap(cmapdata, 32);
 		MakeGoodRemap((uint32_t*)GPalette.BaseColors, GPalette.Remap, cmapdata + 7936);	// last entry in colormap
diff --git a/src/r_data/voxeldef.cpp b/src/r_data/voxeldef.cpp
index a2eee3c35..14f3c8db1 100644
--- a/src/r_data/voxeldef.cpp
+++ b/src/r_data/voxeldef.cpp
@@ -50,8 +50,6 @@
 #include "g_level.h"
 #include "r_data/sprites.h"
 
-using namespace FileSys;
-
 struct VoxelOptions
 {
 	int			DroppedSpin = 0;
@@ -282,7 +280,7 @@ void R_InitVoxels()
 
 			sc.SetCMode(true);
 			sc.MustGetToken(TK_StringConst);
-			voxelfile = fileSystem.CheckNumForFullName(sc.String, true, ns_voxels);
+			voxelfile = fileSystem.CheckNumForAnyName(sc.String, ns_voxels);
 			if (voxelfile < 0)
 			{
 				sc.ScriptMessage("Voxel \"%s\" not found.\n", sc.String);
diff --git a/src/rendering/swrenderer/r_swcolormaps.cpp b/src/rendering/swrenderer/r_swcolormaps.cpp
index 1ff95c8b3..b22895485 100644
--- a/src/rendering/swrenderer/r_swcolormaps.cpp
+++ b/src/rendering/swrenderer/r_swcolormaps.cpp
@@ -346,9 +346,9 @@ void SetDefaultColormap (const char *name)
 		uint8_t unremap[256];
 		uint8_t remap[256];
 
-		lump = fileSystem.CheckNumForFullName (name, true, FileSys::ns_colormaps);
+		lump = fileSystem.CheckNumForAnyName (name, ns_colormaps);
 		if (lump == -1)
-			lump = fileSystem.CheckNumForName (name, FileSys::ns_global);
+			lump = fileSystem.CheckNumForName (name, ns_global);
 
 		// [RH] If using BUILD's palette, generate the colormap
 		if (lump == -1 || fileSystem.CheckNumForFullName("palette.dat") >= 0 || fileSystem.CheckNumForFullName("blood.pal") >= 0)
diff --git a/src/scripting/decorate/thingdef_parse.cpp b/src/scripting/decorate/thingdef_parse.cpp
index 03a249814..53d8ea9b7 100644
--- a/src/scripting/decorate/thingdef_parse.cpp
+++ b/src/scripting/decorate/thingdef_parse.cpp
@@ -1282,7 +1282,7 @@ void ParseDecorate (FScanner &sc, PNamespace *ns)
 			// This check needs to remain overridable for testing purposes.
 			if (fileSystem.GetFileContainer(sc.LumpNum) == 0 && !Args->CheckParm("-allowdecoratecrossincludes"))
 			{
-				int includefile = fileSystem.GetFileContainer(fileSystem.CheckNumForFullName(sc.String, true));
+				int includefile = fileSystem.GetFileContainer(fileSystem.CheckNumForAnyName(sc.String));
 				if (includefile != 0)
 				{
 					I_FatalError("File %s is overriding core lump %s.",
diff --git a/src/sound/s_advsound.cpp b/src/sound/s_advsound.cpp
index 8717c4b9e..1af1ddb1d 100644
--- a/src/sound/s_advsound.cpp
+++ b/src/sound/s_advsound.cpp
@@ -51,8 +51,6 @@
 #include "s_music.h"
 #include "i_music.h"
 
-using namespace FileSys;
-
 // MACROS ------------------------------------------------------------------
 
 #define RANDOM		1
@@ -416,7 +414,7 @@ DEFINE_ACTION_FUNCTION(DObject,S_GetLength)
 
 FSoundID S_AddSound (const char *logicalname, const char *lumpname, FScanner *sc)
 {
-	int lump = fileSystem.CheckNumForFullName (lumpname, true, ns_sounds);
+	int lump = fileSystem.CheckNumForAnyName (lumpname, ns_sounds);
 	return S_AddSound (logicalname, lump);
 }
 
@@ -482,7 +480,7 @@ FSoundID S_AddPlayerSound (const char *pclass, int gender, FSoundID refid, const
 	
 	if (lumpname)
 	{
-		lump = fileSystem.CheckNumForFullName (lumpname, true, ns_sounds);
+		lump = fileSystem.CheckNumForAnyName (lumpname, ns_sounds);
 	}
 
 	return S_AddPlayerSound (pclass, gender, refid, lump);
@@ -1071,7 +1069,7 @@ static void S_AddSNDINFO (int lump)
 				FName mapped = sc.String;
 
 				// only set the alias if the lump it maps to exists.
-				if (mapped == NAME_None || fileSystem.CheckNumForFullName(sc.String, true, ns_music) >= 0)
+				if (mapped == NAME_None || fileSystem.CheckNumForAnyName(sc.String, ns_music) >= 0)
 				{
 					MusicAliases[alias] = mapped;
 				}
diff --git a/src/sound/s_doomsound.cpp b/src/sound/s_doomsound.cpp
index 749b1f5e7..22f99201d 100644
--- a/src/sound/s_doomsound.cpp
+++ b/src/sound/s_doomsound.cpp
@@ -186,7 +186,7 @@ static FString LookupMusic(const char* musicname, int& order)
 static int FindMusic(const char* musicname)
 {
 	int lumpnum = fileSystem.CheckNumForFullName(musicname);
-	if (lumpnum == -1) lumpnum = fileSystem.CheckNumForName(musicname, FileSys::ns_music);
+	if (lumpnum == -1) lumpnum = fileSystem.CheckNumForName(musicname, ns_music);
 	return lumpnum;
 }
 
@@ -295,7 +295,7 @@ void S_Start()
 			if (LocalSndInfo.IsNotEmpty())
 			{
 				// Now parse the local SNDINFO
-				int j = fileSystem.CheckNumForFullName(LocalSndInfo.GetChars(), true);
+				int j = fileSystem.CheckNumForAnyName(LocalSndInfo.GetChars());
 				if (j >= 0) S_AddLocalSndInfo(j);
 			}
 
@@ -309,7 +309,7 @@ void S_Start()
 
 		if (parse_ss)
 		{
-			S_ParseSndSeq(LocalSndSeq.IsNotEmpty() ? fileSystem.CheckNumForFullName(LocalSndSeq.GetChars(), true) : -1);
+			S_ParseSndSeq(LocalSndSeq.IsNotEmpty() ? fileSystem.CheckNumForAnyName(LocalSndSeq.GetChars()) : -1);
 		}
 
 		LastLocalSndInfo = LocalSndInfo;
diff --git a/src/wi_stuff.cpp b/src/wi_stuff.cpp
index 3af0a7829..53d079318 100644
--- a/src/wi_stuff.cpp
+++ b/src/wi_stuff.cpp
@@ -517,7 +517,7 @@ bool DInterBackground::LoadBackground(bool isenterpic)
 	{
 		try
 		{
-			int lumpnum = fileSystem.CheckNumForFullName(lumpname, true);
+			int lumpnum = fileSystem.CheckNumForAnyName(lumpname);
 			if (lumpnum == -1)
 			{
 				I_Error("Intermission animation lump %s not found!", lumpname);
@@ -757,7 +757,7 @@ bool DInterBackground::LoadBackground(bool isenterpic)
 	}
 	else
 	{
-		int lumpnum = fileSystem.CheckNumForFullName(lumpname + 1, true);
+		int lumpnum = fileSystem.CheckNumForAnyName(lumpname + 1);
 		if (lumpnum >= 0)
 		{
 			FScanner sc(lumpnum);