diff --git a/src/common/filesystem/include/fs_filesystem.h b/src/common/filesystem/include/fs_filesystem.h
index bf3fe0e2b..bfd134758 100644
--- a/src/common/filesystem/include/fs_filesystem.h
+++ b/src/common/filesystem/include/fs_filesystem.h
@@ -119,7 +119,7 @@ public:
 
 	static uint32_t LumpNameHash (const char *name);		// [RH] Create hash key from an 8-char name
 
-	int FileLength (int lump) const;
+	ptrdiff_t FileLength (int lump) const;
 	int GetFileFlags (int lump);					// Return the flags for this lump
 	const char* GetFileShortName(int lump) const;
 	const char *GetFileFullName (int lump, bool returnshort = true) const;	// [RH] Returns the lump's full name
diff --git a/src/common/filesystem/source/ancientzip.cpp b/src/common/filesystem/source/ancientzip.cpp
index b95d424a3..34356306e 100644
--- a/src/common/filesystem/source/ancientzip.cpp
+++ b/src/common/filesystem/source/ancientzip.cpp
@@ -167,7 +167,7 @@ unsigned int FZipExploder::InitTable(std::vector<HuffNode> &decoder, int numspot
 	size_t start = decoder.size();
 	decoder.resize(decoder.size() + numspots);
 	memset(&decoder[start], 0, sizeof(HuffNode)*numspots);
-	return start;
+	return (unsigned)start;
 }
 
 int FZipExploder::buildercmp(const void *a, const void *b)
diff --git a/src/common/filesystem/source/file_hog.cpp b/src/common/filesystem/source/file_hog.cpp
index f81c921c6..cc4eef4ff 100644
--- a/src/common/filesystem/source/file_hog.cpp
+++ b/src/common/filesystem/source/file_hog.cpp
@@ -73,7 +73,7 @@ static bool OpenHog(FResourceFile* rf, LumpFilterInfo* filter)
         entries.push_back(Entry);
         Reader->Seek(elength, FileReader::SeekCur);
     }
-    auto Entries = rf->AllocateEntries(entries.size());
+    auto Entries = rf->AllocateEntries((int)entries.size());
     memcpy(Entries, entries.data(), entries.size() * sizeof(Entries[0]));
     rf->GenerateHash();
     return true;
diff --git a/src/common/filesystem/source/filesystem.cpp b/src/common/filesystem/source/filesystem.cpp
index e2be0b187..394735d85 100644
--- a/src/common/filesystem/source/filesystem.cpp
+++ b/src/common/filesystem/source/filesystem.cpp
@@ -774,14 +774,14 @@ int FileSystem::GetResource (int resid, const char *type, int filenum) const
 //
 //==========================================================================
 
-int FileSystem::FileLength (int lump) const
+ptrdiff_t FileSystem::FileLength (int lump) const
 {
 	if ((size_t)lump >= NumEntries)
 	{
 		return -1;
 	}
 	const auto &lump_p = FileInfo[lump];
-	return lump_p.resfile->Length(lump_p.resindex);
+	return (int)lump_p.resfile->Length(lump_p.resindex);
 }
 
 //==========================================================================
diff --git a/src/common/filesystem/source/unicode.cpp b/src/common/filesystem/source/unicode.cpp
index 7b5fd2aef..3d148270a 100644
--- a/src/common/filesystem/source/unicode.cpp
+++ b/src/common/filesystem/source/unicode.cpp
@@ -151,7 +151,7 @@ bool unicode_validate(const char* str)
 	while (*str != 0)
 	{
 		int cp;
-		int result = utf8proc_iterate((const uint8_t*)str, -1, &cp);
+		auto result = utf8proc_iterate((const uint8_t*)str, -1, &cp);
 		if (result < 0) return false;
 	}
 	return true;