diff --git a/src/w_wad.c b/src/w_wad.c
index 57bde14c4..1530a4a04 100644
--- a/src/w_wad.c
+++ b/src/w_wad.c
@@ -26,6 +26,18 @@
 #include "lzf.h"
 #endif
 
+#ifndef _FILE_OFFSET_BITS
+#define _FILE_OFFSET_BITS 0
+#endif
+
+#ifndef _LARGEFILE64_SOURCE
+#define _LARGEFILE64_SOURCE
+#endif
+
+#ifndef _LFS64_LARGEFILE
+#define _LFS64_LARGEFILE
+#endif
+
 #include "zlib.h"
 
 #include "doomdef.h"