diff --git a/src/common/filesystem/filesystem.cpp b/src/common/filesystem/filesystem.cpp
index d768d5d287..1671438b53 100644
--- a/src/common/filesystem/filesystem.cpp
+++ b/src/common/filesystem/filesystem.cpp
@@ -40,10 +40,7 @@
 #include <ctype.h>
 #include <string.h>
 
-#include "m_argv.h"
-#include "cmdlib.h"
 #include "filesystem.h"
-
 #include "m_crc32.h"
 
 #if __has_include("md5.h")
@@ -1320,7 +1317,13 @@ void FileSystem::ReadFile (int lump, void *dest)
 
 FileData FileSystem::ReadFile (int lump)
 {
-	return FileData(FString(*this, ELumpNum(lump)));
+	if ((unsigned)lump >= (unsigned)FileInfo.size())
+	{
+		throw FileSystemException("ReadFile: %u >= NumEntries", lump);
+	}
+	auto lumpp = FileInfo[lump].lump;
+
+	return FileData(lumpp);
 }
 
 //==========================================================================
@@ -1522,10 +1525,6 @@ bool FileSystem::CreatePathlessCopy(const char *name, int id, int /*flags*/)
 
 // FileData -----------------------------------------------------------------
 
-FileData::FileData ()
-{
-}
-
 FileData::FileData (const FileData &copy)
 {
 	Block = copy.Block;
@@ -1537,29 +1536,15 @@ FileData &FileData::operator = (const FileData &copy)
 	return *this;
 }
 
-FileData::FileData (const FString &source)
-: Block (source)
+FileData::FileData (FResourceLump* lump)
 {
+	auto size = lump->LumpSize;
+	Block.resize(1 + size);
+	memcpy(Block.data(), lump->Lock(), size);
+	Block[size] = 0;
+	lump->Unlock();
 }
 
-FileData::~FileData ()
-{
-}
-
-FString::FString (FileSystem& fileSystem, ELumpNum lumpnum)
-{
-	auto lumpr = fileSystem.OpenFileReader ((int)lumpnum);
-	auto size = lumpr.GetLength ();
-	AllocBuffer (1 + size);
-	auto numread = lumpr.Read (&Chars[0], size);
-	Chars[size] = '\0';
-
-	if (numread != size)
-	{
-		throw FileSystemException("ConstructStringFromLump: Only read %ld of %ld bytes on lump %i (%s)\n",
-			numread, size, lumpnum, fileSystem.GetFileFullName((int)lumpnum));
-	}
-}
 
 //==========================================================================
 //
diff --git a/src/common/filesystem/filesystem.h b/src/common/filesystem/filesystem.h
index 9845757e3b..f286669070 100644
--- a/src/common/filesystem/filesystem.h
+++ b/src/common/filesystem/filesystem.h
@@ -29,19 +29,18 @@ union LumpShortName
 class FileData
 {
 public:
-	FileData ();
-
+	FileData () = default;
 	FileData (const FileData &copy);
 	FileData &operator= (const FileData &copy);
-	~FileData ();
-	const void *GetMem () { return Block.Len() == 0 ? NULL : (void *)Block.GetChars(); }
-	size_t GetSize () { return Block.Len(); }
-	const char* GetString () const { return Block.GetChars(); }
+	const void *GetMem () { return Block.size() <= 1 ? NULL : (void *)Block.data(); }
+	size_t GetSize () { return Block.size(); }
+	const char* GetString () const { return (const char*)Block.data(); }
+	const uint8_t* GetBytes() const { return Block.data(); }
 
 private:
-	FileData (const FString &source);
+	FileData (FResourceLump* lump);
 
-	FString Block;
+	std::vector<uint8_t> Block;
 
 	friend class FileSystem;
 };
diff --git a/src/common/fonts/singlelumpfont.cpp b/src/common/fonts/singlelumpfont.cpp
index 94cbd18ecc..72a3b18053 100644
--- a/src/common/fonts/singlelumpfont.cpp
+++ b/src/common/fonts/singlelumpfont.cpp
@@ -125,7 +125,7 @@ FSingleLumpFont::FSingleLumpFont (const char *name, int lump) : FFont(lump)
 	FontName = name;
 
 	FileData data1 = fileSystem.ReadFile (lump);
-	const uint8_t *data = (const uint8_t *)data1.GetMem();
+	auto data = data1.GetBytes();
 
 	if (data[0] == 0xE1 && data[1] == 0xE6 && data[2] == 0xD5 && data[3] == 0x1A)
 	{
@@ -475,7 +475,7 @@ void FSingleLumpFont::LoadBMF(int lump, const uint8_t *data)
 void FSingleLumpFont::CheckFON1Chars()
 {
 	FileData memLump = fileSystem.ReadFile(Lump);
-	const uint8_t* data = (const uint8_t*)memLump.GetMem();
+	auto data = memLump.GetBytes();
 	const uint8_t* data_p;
 
 	data_p = data + 8;
diff --git a/src/common/models/model.cpp b/src/common/models/model.cpp
index c93fa78767..ceb77bcffd 100644
--- a/src/common/models/model.cpp
+++ b/src/common/models/model.cpp
@@ -173,7 +173,7 @@ unsigned FindModel(const char * path, const char * modelfile, bool silent)
 
 	int len = fileSystem.FileLength(lump);
 	FileData lumpd = fileSystem.ReadFile(lump);
-	char * buffer = (char*)lumpd.GetMem();
+	const char * buffer = lumpd.GetString();
 
 	if ( (size_t)fullname.LastIndexOf("_d.3d") == fullname.Len()-5 )
 	{
diff --git a/src/common/models/model_ue1.h b/src/common/models/model_ue1.h
index 9b529b44c7..4163dd2ba8 100644
--- a/src/common/models/model_ue1.h
+++ b/src/common/models/model_ue1.h
@@ -70,15 +70,15 @@ private:
 	{
 		uint16_t numframes, framesize;
 	};
-	d3dhead * dhead;
-	d3dpoly * dpolys;
-	a3dhead * ahead;
-	uint32_t * averts;
+	const d3dhead * dhead;
+	const d3dpoly * dpolys;
+	const a3dhead * ahead;
+	const uint32_t * averts;
 	struct dxvert
 	{
 		int16_t x, y, z, pad;
 	};
-	dxvert * dxverts;
+	const dxvert * dxverts;
 
 	// converted data structures
 	struct UE1Vertex
diff --git a/src/common/models/models_md2.cpp b/src/common/models/models_md2.cpp
index 56ab6274c1..0dd402cf91 100644
--- a/src/common/models/models_md2.cpp
+++ b/src/common/models/models_md2.cpp
@@ -178,7 +178,7 @@ void FDMDModel::LoadGeometry()
 {
 	static int axis[3] = { VX, VY, VZ };
 	FileData lumpdata = fileSystem.ReadFile(mLumpNum);
-	const char *buffer = (const char *)lumpdata.GetMem();
+	auto buffer = lumpdata.GetString();
 	texCoords = new FTexCoord[info.numTexCoords];
 	memcpy(texCoords, buffer + info.offsetTexCoords, info.numTexCoords * sizeof(FTexCoord));
 
@@ -502,7 +502,7 @@ void FMD2Model::LoadGeometry()
 	static int axis[3] = { VX, VY, VZ };
 	uint8_t   *md2_frames;
 	FileData lumpdata = fileSystem.ReadFile(mLumpNum);
-	const char *buffer = (const char *)lumpdata.GetMem();
+	auto buffer = lumpdata.GetString();
 
 	texCoords = new FTexCoord[info.numTexCoords];
 	memcpy(texCoords, (uint8_t*)buffer + info.offsetTexCoords, info.numTexCoords * sizeof(FTexCoord));
diff --git a/src/common/models/models_md3.cpp b/src/common/models/models_md3.cpp
index 2337a38973..ea2083a8ba 100644
--- a/src/common/models/models_md3.cpp
+++ b/src/common/models/models_md3.cpp
@@ -190,7 +190,7 @@ bool FMD3Model::Load(const char * path, int lumpnum, const char * buffer, int le
 void FMD3Model::LoadGeometry()
 {
 	FileData lumpdata = fileSystem.ReadFile(mLumpNum);
-	const char *buffer = (const char *)lumpdata.GetMem();
+	auto buffer = lumpdata.GetString();
 	md3_header_t * hdr = (md3_header_t *)buffer;
 	md3_surface_t * surf = (md3_surface_t*)(buffer + LittleLong(hdr->Ofs_Surfaces));
 
diff --git a/src/common/models/models_ue1.cpp b/src/common/models/models_ue1.cpp
index 5db36a672b..aa85678508 100644
--- a/src/common/models/models_ue1.cpp
+++ b/src/common/models/models_ue1.cpp
@@ -69,26 +69,25 @@ bool FUE1Model::Load( const char *filename, int lumpnum, const char *buffer, int
 
 void FUE1Model::LoadGeometry()
 {
-	FileData lump, lump2;
 	const char *buffer, *buffer2;
-	lump = fileSystem.ReadFile(mDataLump);
-	buffer = (char*)lump.GetMem();
-	lump2 = fileSystem.ReadFile(mAnivLump);
-	buffer2 = (char*)lump2.GetMem();
+	FileData lump = fileSystem.ReadFile(mDataLump);
+	buffer = lump.GetString();
+	FileData lump2 = fileSystem.ReadFile(mAnivLump);
+	buffer2 = lump2.GetString();
 	// map structures
-	dhead = (d3dhead*)(buffer);
-	dpolys = (d3dpoly*)(buffer+sizeof(d3dhead));
-	ahead = (a3dhead*)(buffer2);
+	dhead = (const d3dhead*)(buffer);
+	dpolys = (const d3dpoly*)(buffer+sizeof(d3dhead));
+	ahead = (const a3dhead*)(buffer2);
 	// detect deus ex format
 	if ( (ahead->framesize/dhead->numverts) == 8 )
 	{
-		averts = NULL;
-		dxverts = (dxvert*)(buffer2+sizeof(a3dhead));
+		averts = nullptr;
+		dxverts = (const dxvert*)(buffer2+sizeof(a3dhead));
 	}
 	else
 	{
-		averts = (uint32_t*)(buffer2+sizeof(a3dhead));
-		dxverts = NULL;
+		averts = (const uint32_t*)(buffer2+sizeof(a3dhead));
+		dxverts = nullptr;
 	}
 	// set counters
 	numVerts = dhead->numverts;
diff --git a/src/common/models/voxels.cpp b/src/common/models/voxels.cpp
index d8d2b22454..6c7867ccf2 100644
--- a/src/common/models/voxels.cpp
+++ b/src/common/models/voxels.cpp
@@ -162,7 +162,7 @@ FVoxel *R_LoadKVX(int lumpnum)
 	int i, j, n;
 
 	FileData lump = fileSystem.ReadFile(lumpnum);	// FileData adds an extra 0 byte to the end.
-	uint8_t *rawvoxel = (uint8_t *)lump.GetMem();
+	auto rawvoxel = lump.GetBytes();
 	int voxelsize = (int)(lump.GetSize()-1);
 
 	// Oh, KVX, why couldn't you have a proper header? We'll just go through
diff --git a/src/common/textures/formats/automaptexture.cpp b/src/common/textures/formats/automaptexture.cpp
index c253650fda..6b660b1bac 100644
--- a/src/common/textures/formats/automaptexture.cpp
+++ b/src/common/textures/formats/automaptexture.cpp
@@ -93,7 +93,7 @@ PalettedPixels FAutomapTexture::CreatePalettedPixels(int conversion)
 {
 	int x, y;
 	FileData data = fileSystem.ReadFile (SourceLump);
-	const uint8_t *indata = (const uint8_t *)data.GetMem();
+	auto indata = data.GetBytes();
 
 	PalettedPixels Pixels(Width * Height);
 
diff --git a/src/common/textures/formats/imgztexture.cpp b/src/common/textures/formats/imgztexture.cpp
index 733d20f844..fb020c9a10 100644
--- a/src/common/textures/formats/imgztexture.cpp
+++ b/src/common/textures/formats/imgztexture.cpp
@@ -121,7 +121,7 @@ FIMGZTexture::FIMGZTexture (int lumpnum, uint16_t w, uint16_t h, int16_t l, int1
 PalettedPixels FIMGZTexture::CreatePalettedPixels(int conversion)
 {
 	FileData lump = fileSystem.ReadFile (SourceLump);
-	const ImageHeader *imgz = (const ImageHeader *)lump.GetMem();
+	auto imgz = (const ImageHeader *)lump.GetMem();
 	const uint8_t *data = (const uint8_t *)&imgz[1];
 
 	uint8_t *dest_p;
diff --git a/src/common/textures/formats/qoitexture.cpp b/src/common/textures/formats/qoitexture.cpp
index abe6282230..c84ac38ce3 100644
--- a/src/common/textures/formats/qoitexture.cpp
+++ b/src/common/textures/formats/qoitexture.cpp
@@ -148,7 +148,7 @@ int FQOITexture::CopyPixels(FBitmap *bmp, int conversion)
 	size_t p = 14, run = 0;
 
 	size_t chunks_len = lump.GetSize() - 8;
-	auto bytes = (const uint8_t*)lump.GetMem();
+	auto bytes = lump.GetBytes();
 
 	for (int h = 0; h < Height; h++)
 	{
diff --git a/src/common/textures/formats/rawpagetexture.cpp b/src/common/textures/formats/rawpagetexture.cpp
index 337ca55209..e2b6c11466 100644
--- a/src/common/textures/formats/rawpagetexture.cpp
+++ b/src/common/textures/formats/rawpagetexture.cpp
@@ -173,7 +173,7 @@ FRawPageTexture::FRawPageTexture (int lumpnum)
 PalettedPixels FRawPageTexture::CreatePalettedPixels(int conversion)
 {
 	FileData lump = fileSystem.ReadFile (SourceLump);
-	const uint8_t *source = (const uint8_t *)lump.GetMem();
+	auto source = lump.GetBytes();
 	const uint8_t *source_p = source;
 	uint8_t *dest_p;
 
@@ -206,8 +206,8 @@ int FRawPageTexture::CopyPixels(FBitmap *bmp, int conversion)
 	{
 		FileData lump = fileSystem.ReadFile(SourceLump);
 		FileData plump = fileSystem.ReadFile(mPaletteLump);
-		const uint8_t *source = (const uint8_t *)lump.GetMem();
-		const uint8_t *psource = (const uint8_t *)plump.GetMem();
+		auto source = lump.GetBytes();
+		auto psource = plump.GetBytes();
 		PalEntry paldata[256];
 		for (auto & pe : paldata)
 		{
diff --git a/src/common/textures/formats/startuptexture.cpp b/src/common/textures/formats/startuptexture.cpp
index 8a2a1e602f..718b7182a2 100644
--- a/src/common/textures/formats/startuptexture.cpp
+++ b/src/common/textures/formats/startuptexture.cpp
@@ -165,7 +165,7 @@ FStartupTexture::FStartupTexture (int lumpnum)
 	bUseGamePalette = false;
 	
 	FileData lump = fileSystem.ReadFile (SourceLump);
-	const uint8_t *source = (const uint8_t *)lump.GetMem();
+	auto source = lump.GetBytes();
 
 	// Initialize the bitmap palette.
 	// the palette is static so that the notches can share it.
@@ -234,7 +234,7 @@ void PlanarToChunky(T* dest, const uint8_t* src, const T* remap, int width, int
 PalettedPixels FStartupTexture::CreatePalettedPixels(int conversion)
 {
 	FileData lump = fileSystem.ReadFile (SourceLump);
-	const uint8_t *source = (const uint8_t *)lump.GetMem();
+	auto source = lump.GetBytes();
 	const uint8_t *remap = ImageHelpers::GetRemap(conversion == luminance);
 
 
@@ -254,7 +254,7 @@ PalettedPixels FStartupTexture::CreatePalettedPixels(int conversion)
 int FStartupTexture::CopyPixels(FBitmap *bmp, int conversion)
 {
 	FileData lump = fileSystem.ReadFile (SourceLump);
-	const uint8_t *source = (const uint8_t *)lump.GetMem();
+	auto source = lump.GetBytes();
 	PlanarToChunky((uint32_t*)bmp->GetPixels(), source + 48, startuppalette32, Width, Height);
 	return 0;
 }
@@ -282,7 +282,7 @@ FNotchTexture::FNotchTexture (int lumpnum, int width, int height)
 PalettedPixels FNotchTexture::CreatePalettedPixels(int conversion)
 {
 	FileData lump = fileSystem.ReadFile (SourceLump);
-	const uint8_t *source = (const uint8_t *)lump.GetMem();
+	auto source = lump.GetBytes();
 	const uint8_t *remap = ImageHelpers::GetRemap(conversion == luminance);
 
 	TArray<uint8_t> Work(Width*Height, true);
@@ -305,7 +305,7 @@ PalettedPixels FNotchTexture::CreatePalettedPixels(int conversion)
 int FNotchTexture::CopyPixels(FBitmap *bmp, int conversion)
 {
 	FileData lump = fileSystem.ReadFile (SourceLump);
-	const uint8_t *source = (const uint8_t *)lump.GetMem();
+	auto source = lump.GetBytes();
 
 	auto Work = (uint32_t*)bmp->GetPixels();
 	for(int i = 0; i < Width * Height / 2; i++)
@@ -339,7 +339,7 @@ FStrifeStartupTexture::FStrifeStartupTexture (int lumpnum, int w, int h)
 PalettedPixels FStrifeStartupTexture::CreatePalettedPixels(int conversion)
 {
 	FileData lump = fileSystem.ReadFile (SourceLump);
-	const uint8_t *source = (const uint8_t *)lump.GetMem();
+	auto source = lump.GetBytes();
 	PalettedPixels Pixels(Width*Height);
 	const uint8_t *remap = ImageHelpers::GetRemap(conversion == luminance);
 	ImageHelpers::FlipNonSquareBlockRemap(Pixels.Data(), source, Width, Height, Width, remap);
diff --git a/src/common/utility/palette.cpp b/src/common/utility/palette.cpp
index 527d1cd173..4d1cd14443 100644
--- a/src/common/utility/palette.cpp
+++ b/src/common/utility/palette.cpp
@@ -663,9 +663,8 @@ int V_GetColorFromString(const char* cstr, FScriptPosition* sc)
 
 FString V_GetColorStringByName(const char* name, FScriptPosition* sc)
 {
-	FileData rgbNames;
-	char* rgbEnd;
-	char* rgb, * endp;
+	const char* rgbEnd;
+	const char* rgb, * endp;
 	int rgblump;
 	int c[3], step;
 	size_t namelen;
@@ -680,7 +679,7 @@ FString V_GetColorStringByName(const char* name, FScriptPosition* sc)
 		return FString();
 	}
 
-	rgbNames = fileSystem.ReadFile(rgblump);
+	auto rgbNames = fileSystem.ReadFile(rgblump);
 	rgb = (char*)rgbNames.GetMem();
 	rgbEnd = rgb + fileSystem.FileLength(rgblump);
 	step = 0;
@@ -705,7 +704,7 @@ FString V_GetColorStringByName(const char* name, FScriptPosition* sc)
 		}
 		else if (step < 3)
 		{ // collect RGB values
-			c[step++] = strtoul(rgb, &endp, 10);
+			c[step++] = strtoul(rgb, (char**)&endp, 10);
 			if (endp == rgb)
 			{
 				break;
@@ -930,7 +929,7 @@ int ReadPalette(int lumpnum, uint8_t* buffer)
 		return 0;
 	}
 	FileData lump = fileSystem.ReadFile(lumpnum);
-	uint8_t* lumpmem = (uint8_t*)lump.GetMem();
+	auto lumpmem = lump.GetBytes();
 	memset(buffer, 0, 768);
 
 	FileReader fr;
diff --git a/src/common/utility/zstring.h b/src/common/utility/zstring.h
index 89ae13568e..1164ddb6d4 100644
--- a/src/common/utility/zstring.h
+++ b/src/common/utility/zstring.h
@@ -147,9 +147,6 @@ public:
 	FString (const char *head, const char *tail);
 	FString (char head, const FString &tail);
 
-	// Other constructors
-	FString (FileSystem&, ELumpNum);	// Create from a lump
-
 	~FString ();
 
 	// Discard string's contents, create a new buffer, and lock it.
diff --git a/src/gamedata/keysections.cpp b/src/gamedata/keysections.cpp
index 5f06f192e6..390c8009f8 100644
--- a/src/gamedata/keysections.cpp
+++ b/src/gamedata/keysections.cpp
@@ -166,8 +166,8 @@ void D_LoadWadSettings ()
 	while ((lump = fileSystem.FindLump ("KEYCONF", &lastlump)) != -1)
 	{
 		FileData data = fileSystem.ReadFile (lump);
-		const char *eof = (char *)data.GetMem() + fileSystem.FileLength (lump);
-		const char *conf = (char *)data.GetMem();
+		const char *eof = data.GetString() + fileSystem.FileLength (lump);
+		const char *conf = data.GetString();
 
 		while (conf < eof)
 		{
diff --git a/src/gamedata/textures/anim_switches.cpp b/src/gamedata/textures/anim_switches.cpp
index 78e49508df..36666bc3f8 100644
--- a/src/gamedata/textures/anim_switches.cpp
+++ b/src/gamedata/textures/anim_switches.cpp
@@ -67,7 +67,7 @@ void FTextureAnimator::InitSwitchList ()
 	if (lump != -1)
 	{
 		FileData lumpdata = fileSystem.ReadFile (lump);
-		const char *alphSwitchList = (const char *)lumpdata.GetMem();
+		auto alphSwitchList = lumpdata.GetString();
 		const char *list_p;
 		FSwitchDef *def1, *def2;
 
diff --git a/src/gamedata/textures/animations.cpp b/src/gamedata/textures/animations.cpp
index 0091a3ba57..51834d4e08 100644
--- a/src/gamedata/textures/animations.cpp
+++ b/src/gamedata/textures/animations.cpp
@@ -205,7 +205,7 @@ void FTextureAnimator::InitAnimated (void)
 	{
 		FileData animatedlump = fileSystem.ReadFile (lumpnum);
 		int animatedlen = fileSystem.FileLength(lumpnum);
-		const uint8_t *animdefs = (const uint8_t *)animatedlump.GetMem();
+		auto animdefs = animatedlump.GetBytes();
 		const uint8_t *anim_p;
 		FTextureID pic1, pic2;
 		int animtype;
diff --git a/src/gamedata/textures/buildloader.cpp b/src/gamedata/textures/buildloader.cpp
index 4bb7b2721a..515635871e 100644
--- a/src/gamedata/textures/buildloader.cpp
+++ b/src/gamedata/textures/buildloader.cpp
@@ -85,7 +85,7 @@ static int BuildPaletteTranslation(int lump)
 	}
 
 	FileData data = fileSystem.ReadFile(lump);
-	const uint8_t *ipal = (const uint8_t *)data.GetMem();
+	auto ipal = data.GetBytes();
 	FRemapTable opal;
 
 	bool blood = false;
diff --git a/src/maploader/glnodes.cpp b/src/maploader/glnodes.cpp
index ff44922795..15b4b46ba8 100644
--- a/src/maploader/glnodes.cpp
+++ b/src/maploader/glnodes.cpp
@@ -754,7 +754,7 @@ static int FindGLNodesInWAD(int labellump)
 				if (fileSystem.GetFileContainer(lump)==wadfile)
 				{
 					FileData mem = fileSystem.ReadFile(lump);
-					if (MatchHeader(fileSystem.GetFileFullName(labellump), (const char *)mem.GetMem())) return lump;
+					if (MatchHeader(fileSystem.GetFileFullName(labellump), mem.GetString())) return lump;
 				}
 			}
 		}
diff --git a/src/r_data/r_translate.cpp b/src/r_data/r_translate.cpp
index 0f130e30a6..1490faf260 100644
--- a/src/r_data/r_translate.cpp
+++ b/src/r_data/r_translate.cpp
@@ -431,7 +431,7 @@ static void R_CreatePlayerTranslation (float h, float s, float v, const FPlayerC
 		else
 		{
 			FileData translump = fileSystem.ReadFile(colorset->Lump);
-			const uint8_t *trans = (const uint8_t *)translump.GetMem();
+			auto trans = translump.GetBytes();
 			for (i = start; i <= end; ++i)
 			{
 				table->Remap[i] = GPalette.Remap[trans[i]];
diff --git a/src/r_data/sprites.cpp b/src/r_data/sprites.cpp
index 97a5e2e46f..1f6b161a98 100644
--- a/src/r_data/sprites.cpp
+++ b/src/r_data/sprites.cpp
@@ -947,7 +947,7 @@ CCMD (skins)
 static void R_CreateSkinTranslation (const char *palname)
 {
 	FileData lump = fileSystem.ReadFile (palname);
-	const uint8_t *otherPal = (uint8_t *)lump.GetMem();
+	auto otherPal = lump.GetBytes();
  
 	for (int i = 0; i < 256; ++i)
 	{
diff --git a/src/r_data/v_palette.cpp b/src/r_data/v_palette.cpp
index 333cb7579b..068edb124a 100644
--- a/src/r_data/v_palette.cpp
+++ b/src/r_data/v_palette.cpp
@@ -63,7 +63,7 @@ void InitPalette ()
 	if (lump != -1)
 	{
 		FileData cmap = fileSystem.ReadFile(lump);
-		const unsigned char* cmapdata = (const unsigned char*)cmap.GetMem();
+		auto cmapdata = cmap.GetBytes();
 		GPalette.GenerateGlobalBrightmapFromColormap(cmapdata, 32);
 		MakeGoodRemap((uint32_t*)GPalette.BaseColors, GPalette.Remap, cmapdata + 7936);	// last entry in colormap
 	}