diff --git a/Quake/sys.h b/Quake/sys.h
index 81cf5f44..9c576e82 100644
--- a/Quake/sys.h
+++ b/Quake/sys.h
@@ -30,7 +30,7 @@ void Sys_Init (void);
 // file IO
 //
 
-typedef long long qfileofs_t;
+typedef int64_t qfileofs_t;
 
 int		   Sys_fseek (FILE *file, qfileofs_t ofs, int origin);
 qfileofs_t Sys_ftell (FILE *file);
diff --git a/Quake/sys_sdl_unix.c b/Quake/sys_sdl_unix.c
index 5ef67329..3c468997 100644
--- a/Quake/sys_sdl_unix.c
+++ b/Quake/sys_sdl_unix.c
@@ -51,12 +51,12 @@ COMPILE_TIME_ASSERT (CHECK_LARGE_FILE_SUPPORT, sizeof (off_t) >= sizeof (qfileof
 
 int Sys_fseek (FILE *file, qfileofs_t ofs, int origin)
 {
-	return fseeko (file, ofs, origin);
+	return fseeko (file, (off_t)ofs, origin);
 }
 
 qfileofs_t Sys_ftell (FILE *file)
 {
-	return ftello (file);
+	return (qfileofs_t)ftello (file);
 }
 
 int Sys_FileType (const char *path)
diff --git a/Quake/sys_sdl_win.c b/Quake/sys_sdl_win.c
index 41d427df..ced949e6 100644
--- a/Quake/sys_sdl_win.c
+++ b/Quake/sys_sdl_win.c
@@ -55,14 +55,16 @@ static HANDLE hinput, houtput;
 static char	  cwd[1024];
 static double counter_freq;
 
+COMPILE_TIME_ASSERT (CHECK_LARGE_FILE_SUPPORT, sizeof (long long) >= sizeof (qfileofs_t));
+
 int Sys_fseek (FILE *file, qfileofs_t ofs, int origin)
 {
-	return _fseeki64 (file, ofs, origin);
+	return _fseeki64 (file, (long long)ofs, origin);
 }
 
 qfileofs_t Sys_ftell (FILE *file)
 {
-	return _ftelli64 (file);
+	return (qfileofs_t)_ftelli64 (file);
 }
 
 static void Sys_GetBasedir (char *argv0, char *dst, size_t dstsize)