diff --git a/net.c b/net.c
index c0b06fd9..3d20422a 100644
--- a/net.c
+++ b/net.c
@@ -870,7 +870,7 @@ handle_request(coap_context_t *context, coap_queue_t *node) {
 					   opt_filter);
     }
       
-    if (coap_send(context, &node->remote, response) == COAP_INVALID_TID) {
+    if (response && coap_send(context, &node->remote, response) == COAP_INVALID_TID) {
       warn("cannot send response for transaction %u\n", node->id);
       coap_delete_pdu(response);
     }
diff --git a/pdu.c b/pdu.c
index bcc511d6..0636a4bf 100644
--- a/pdu.c
+++ b/pdu.c
@@ -27,7 +27,7 @@
 #ifdef WITH_CONTIKI
 #include "memb.h"
 
-typedef unsigned char _pdu[COAP_MAX_PDU_SIZE];
+typedef unsigned char _pdu[sizeof(coap_pdu_t) + COAP_MAX_PDU_SIZE];
 
 MEMB(pdu_storage, _pdu, COAP_PDU_MAXCNT);