diff --git a/sys/include/net/sixlowpan.h b/sys/include/net/sixlowpan.h
index 583903b2f8..eb9bdac4ea 100644
--- a/sys/include/net/sixlowpan.h
+++ b/sys/include/net/sixlowpan.h
@@ -71,7 +71,7 @@ extern "C" {
  */
 static inline bool sixlowpan_nalp(uint8_t disp)
 {
-    return (disp & 0x3f);
+    return ((disp & 0xc0) == 0);
 }
 /** @} */