diff --git a/src/d_main.cpp b/src/d_main.cpp
index a48da088e..b555b6c4c 100644
--- a/src/d_main.cpp
+++ b/src/d_main.cpp
@@ -2498,6 +2498,12 @@ static int D_DoomMain_Internal (void)
 		}
 		lfi.gameTypeFilter.Push(FStringf("game-%s", GameTypeName()));
 
+		static const char* folders[] = { "flats/", "textures/", "hires/", "sprites/", "voxels/", "colormaps/", "acs/", "maps/", "voices/", "patches/", "graphics/", "sounds/", "music/" };
+		for (auto p : folders) lfi.reservedFolders.Push(p);
+
+		static const char* reserved[] = { "mapinfo", "zmapinfo", "gameinfo", "sndinfo", "sbarinfo", "menudef", "gldefs", "animdefs", "decorate", "zscript", "maps/" };
+		for (auto p : reserved) lfi.requiredPrefixes.Push(p);
+
 		Wads.InitMultipleFiles (allwads, iwad_info->DeleteLumps, false, &lfi);
 		allwads.Clear();
 		allwads.ShrinkToFit();
diff --git a/src/gamedata/resourcefiles/file_zip.cpp b/src/gamedata/resourcefiles/file_zip.cpp
index 881b52763..f5fb9f332 100644
--- a/src/gamedata/resourcefiles/file_zip.cpp
+++ b/src/gamedata/resourcefiles/file_zip.cpp
@@ -237,20 +237,7 @@ bool FZipFile::Open(bool quiet, LumpFilterInfo* filter)
 		if (i == 0)
 		{
 			// check for special names, if one of these gets found this must be treated as a normal zip.
-			bool isspecial = !name.Compare("flats/") ||
-				name.IndexOf("/") < 0 ||
-				!name.Compare("textures/") ||
-				!name.Compare("hires/") ||
-				!name.Compare("sprites/") ||
-				!name.Compare("voxels/") ||
-				!name.Compare("colormaps/") ||
-				!name.Compare("acs/") ||
-				!name.Compare("maps/") ||
-				!name.Compare("voices/") ||
-				!name.Compare("patches/") ||
-				!name.Compare("graphics/") ||
-				!name.Compare("sounds/") ||
-				!name.Compare("music/");
+			bool isspecial = name.IndexOf("/") < 0 || (filter && filter->reservedFolders.Find(name) < filter->reservedFolders.Size());
 			if (isspecial) break;
 			name0 = name;
 		}
@@ -261,22 +248,17 @@ bool FZipFile::Open(bool quiet, LumpFilterInfo* filter)
 				name0 = "";
 				break;
 			}
-			else if (!foundspeciallump)
+			else if (!foundspeciallump && filter)
 			{
 				// at least one of the more common definition lumps must be present.
-				if (name.IndexOf(name0 + "mapinfo") == 0) foundspeciallump = true;
-				else if (name.IndexOf(name0 + "zmapinfo") == 0) foundspeciallump = true;
-				else if (name.IndexOf(name0 + "gameinfo") == 0) foundspeciallump = true;
-				else if (name.IndexOf(name0 + "sndinfo") == 0) foundspeciallump = true;
-				else if (name.IndexOf(name0 + "sbarinfo") == 0) foundspeciallump = true;
-				else if (name.IndexOf(name0 + "menudef") == 0) foundspeciallump = true;
-				else if (name.IndexOf(name0 + "gldefs") == 0) foundspeciallump = true;
-				else if (name.IndexOf(name0 + "animdefs") == 0) foundspeciallump = true;
-				else if (name.IndexOf(name0 + "decorate.") == 0) foundspeciallump = true;	// DECORATE is a common subdirectory name, so the check needs to be a bit different.
-				else if (name.Compare(name0 + "decorate") == 0) foundspeciallump = true;
-				else if (name.IndexOf(name0 + "zscript.") == 0) foundspeciallump = true;	// same here.
-				else if (name.Compare(name0 + "zscript") == 0) foundspeciallump = true;
-				else if (name.Compare(name0 + "maps/") == 0) foundspeciallump = true;
+				for (auto &p : filter->requiredPrefixes)
+				{ 
+					if (name.IndexOf(name0 + p) == 0)
+					{
+						foundspeciallump = true;
+						break;
+					}
+				}
 			}
 		}
 	}
diff --git a/src/gamedata/resourcefiles/resourcefile.h b/src/gamedata/resourcefiles/resourcefile.h
index 6bd7fc51f..7bc7aeae6 100644
--- a/src/gamedata/resourcefiles/resourcefile.h
+++ b/src/gamedata/resourcefiles/resourcefile.h
@@ -9,6 +9,10 @@ struct LumpFilterInfo
 {
 	TArray<FString> gameTypeFilter;	// this can contain multiple entries
 	FString dotFilter;
+
+	// The following are for checking if the root directory of a zip can be removed.
+	TArray<FString> reservedFolders;
+	TArray<FString> requiredPrefixes;
 };
 
 class FResourceFile;