diff --git a/src/core/udp.c b/src/core/udp.c
index 2144ae67..070cd375 100644
--- a/src/core/udp.c
+++ b/src/core/udp.c
@@ -415,14 +415,17 @@ udp_send(struct udp_pcb *pcb, struct pbuf *p)
   if (q != p) {
     /* chained header still in front of given pbuf? */
     if (q->next == p) {
-      DEBUGF(UDP_DEBUG, ("udp_send: dechaining and freeing header pbuf\n"));
+      DEBUGF(UDP_DEBUG | DBG_TRACE | 2, ("udp_send: dechaining and freeing header pbuf %p\n", (void *)q));
       /* detach the header prepended earlier */
       pbuf_dechain(q);
       /* free the header */
       pbuf_free(q);
     } else {
-      DEBUGF(UDP_DEBUG, ("udp_send: pbuf header not freed, seems to be queued.\n"));
-	}
+      /* the header now points to something else then the given pbuf */
+      /* this can only happen if queueing is enabled */
+      LWIP_ASSERT("ARP_QUEUEING == 1\n", ARP_QUEUEING == 1);
+      DEBUGF(UDP_DEBUG | DBG_TRACE | 2, ("udp_send: pbuf header %p not freed, seems queued.\n", (void *)q));
+   	}
   }
   
 #ifdef UDP_STATS