diff --git a/src/include/lwip/def.h b/src/include/lwip/def.h
index 6cc41380..8464f105 100644
--- a/src/include/lwip/def.h
+++ b/src/include/lwip/def.h
@@ -32,6 +32,9 @@
 #ifndef __LWIP_DEF_H__
 #define __LWIP_DEF_H__
 
+/* this might define NULL already */
+#include "arch/cc.h"
+
 #define UMAX(a, b)      ((a) > (b) ? (a) : (b))
 
 #ifndef NULL