--- a/bindings/python/ns3modulegen_core_customizations.py	Tue Aug 13 22:54:45 2013 -0700
+++ b/bindings/python/ns3modulegen_core_customizations.py	Tue Aug 13 22:56:39 2013 -0700
@@ -177,8 +177,11 @@
     }
     virtual ~%s()
     {
+        PyGILState_STATE __py_gil_state;
+        __py_gil_state = (PyEval_ThreadsInitialized() ? PyGILState_Ensure() : (PyGILState_STATE) 0);
         Py_DECREF(m_callback);
         m_callback = NULL;
+        PyGILState_Release(__py_gil_state);
     }
 
     virtual bool IsEqual(ns3::Ptr<const ns3::CallbackImplBase> other_base) const