diff --git a/core/lib/rand.c b/core/lib/rand.c
index 2a1869328..54c1681fb 100644
--- a/core/lib/rand.c
+++ b/core/lib/rand.c
@@ -28,11 +28,18 @@
  *
  * This file is part of the Contiki operating system.
  *
- * @(#)$Id: rand.c,v 1.4 2007/06/01 15:28:02 bg- Exp $
+ * @(#)$Id: rand.c,v 1.5 2007/06/04 18:03:58 bg- Exp $
  */
 
 #include <stdlib.h>
 
+#include "lib/assert.h"
+
+#ifdef RAND_MAX
+/* Use rand() from libc if this breaks! */
+CTASSERT(RAND_MAX == 0x7fff);
+#endif
+
 #include "rand.h"
 
 /*