diff --git a/libs/ardour/graph.cc b/libs/ardour/graph.cc
index 3eb601e82b..3ec912ecd3 100644
--- a/libs/ardour/graph.cc
+++ b/libs/ardour/graph.cc
@@ -583,10 +583,12 @@ Graph::process_one_route (Route* route)
 bool
 Graph::in_process_thread () const
 {
+#ifndef WIN32
 	for (list<pthread_t>::const_iterator i = _thread_list.begin (); i != _thread_list.end(); ++i) {
 		if (*i == pthread_self()) {
 			return true;
 		}
 	}
 	return false;
+#endif
 }