diff --git a/sys/net/application_layer/nanocoap/sock.c b/sys/net/application_layer/nanocoap/sock.c
index e77e9e94d3..446adb1957 100644
--- a/sys/net/application_layer/nanocoap/sock.c
+++ b/sys/net/application_layer/nanocoap/sock.c
@@ -145,6 +145,9 @@ int nanocoap_server(sock_udp_ep_t *local, uint8_t *buf, size_t bufsize)
             if ((res = coap_handle_req(&pkt, buf, bufsize)) > 0) {
                 res = sock_udp_send(&sock, buf, res, &remote);
             }
+            else {
+                DEBUG("error handling request %d\n", (int)res);
+            }
         }
     }