diff --git a/mozilla/include/xp_core.h b/mozilla/include/xp_core.h
index 6a839decf97..4413ca93e7d 100644
--- a/mozilla/include/xp_core.h
+++ b/mozilla/include/xp_core.h
@@ -248,9 +248,13 @@ typedef int (*FARPROC)();
 #ifndef _INT32
 #define _INT32
 #endif
+#ifndef _UINT16
 #define _UINT16
+#endif
+#ifndef _UINT32
 #define _UINT32
 #endif
+#endif
 
 /* function classifications */