diff --git a/am/am.h b/am/am.h
index bad1376b915f65e5576b4c715ec1b65dc43823cc..bc7fc40f4a31519033fd2a101ea91bdc4ded2113 100755
--- a/am/am.h
+++ b/am/am.h
@@ -10,6 +10,10 @@
 #include <stdint.h>
 #include <arch.h>
 
+#ifndef NULL
+# define NULL ((void *)0)
+#endif
+
 #define MAX_CPU 8
 
 typedef struct _Area {