diff --git a/common/JackAPI.cpp b/common/JackAPI.cpp
index 13b99160..d90558bb 100644
--- a/common/JackAPI.cpp
+++ b/common/JackAPI.cpp
@@ -555,8 +555,9 @@ EXPORT int jack_port_set_name(jack_port_t* port, const char* name)
         return -1;
     } else {
         JackGraphManager* manager = GetGraphManager();
-        if (manager) {
-            JackClient* client = JackClient::fClientTable[manager->GetPort(myport)->GetRefNum()];
+        int refnum;
+        if (manager && ((refnum = manager->GetPort(myport)->GetRefNum()) > 0)) {
+            JackClient* client = JackClient::fClientTable[refnum];
             assert(client);
             return client->PortRename(myport, name);
         } else {
diff --git a/common/JackClient.cpp b/common/JackClient.cpp
index 36b6981f..1ba01a8c 100644
--- a/common/JackClient.cpp
+++ b/common/JackClient.cpp
@@ -244,7 +244,7 @@ int JackClient::ClientNotify(int refnum, const char* name, int notify, int sync,
                 break;
                 
              case kPortRenameCallback:
-                jack_log("JackClient::kPortRenameCallback src = %ld dst = %ld", value1, value2);
+                jack_log("JackClient::kPortRenameCallback port = %ld");
                 if (fPortRename)
                     fPortRename(value1, GetGraphManager()->GetPort(value1)->GetName(), fPortRenameArg);
                 break;
diff --git a/common/jack/jack.h b/common/jack/jack.h
index 76c1243c..d5336259 100644
--- a/common/jack/jack.h
+++ b/common/jack/jack.h
@@ -416,7 +416,7 @@ extern "C"
      *
      * @return 0 on success, otherwise a non-zero error code
      */
-    int jack_set_port_registration_callback (jack_client_t *,
+     int jack_set_port_registration_callback (jack_client_t *,
             JackPortRegistrationCallback
             registration_callback, void *arg);