diff --git a/functions.h b/functions.h
index 2659b4bf43..04d255f29f 100644
--- a/functions.h
+++ b/functions.h
@@ -257,7 +257,7 @@ void GameSizeChanged(void);
 bool FileExists(const char *filename);
 bool ReadLanguagePack(int index);
 void InitializeLanguagePacks(void);
-byte *ReadFileToMem(const char *filename, size_t *lenp, size_t maxsize);
+void *ReadFileToMem(const char *filename, size_t *lenp, size_t maxsize);
 int GetLanguageList(char **languages, int max);
 
 void CheckSwitchToEuro(void);
diff --git a/ttd.c b/ttd.c
index 46e9b2d100..07544364b9 100644
--- a/ttd.c
+++ b/ttd.c
@@ -218,7 +218,7 @@ static char *strecpy(char *dst, const char *src)
 	return dst - 1;
 }
 
-byte *ReadFileToMem(const char *filename, size_t *lenp, size_t maxsize)
+void *ReadFileToMem(const char *filename, size_t *lenp, size_t maxsize)
 {
 	FILE *in;
 	byte *mem;