diff --git a/common/JackEngine.cpp b/common/JackEngine.cpp
index 998cb651..6a511f3f 100644
--- a/common/JackEngine.cpp
+++ b/common/JackEngine.cpp
@@ -804,6 +804,9 @@ int JackEngine::PortRegister(int refnum, const char* name, const char *type, uns
         return -1;
     }
 
+    if (! buffer_size) {
+        buffer_size = fEngineControl->fBufferSize;
+    }
     *port_index = fGraphManager->AllocatePort(refnum, name, type, (JackPortFlags)flags, buffer_size);
     if (*port_index != NO_PORT) {
         if (client->GetClientControl()->fActive)