diff --git a/libs/pbd/pbd/abstract_ui.h b/libs/pbd/pbd/abstract_ui.h
index 8e386aa4eb..a8602c7d78 100644
--- a/libs/pbd/pbd/abstract_ui.h
+++ b/libs/pbd/pbd/abstract_ui.h
@@ -75,8 +75,20 @@ class ABSTRACT_UI_API AbstractUI : public BaseUI
         };
 	typedef typename RequestBuffer::rw_vector RequestBufferVector;
 
+#if defined(COMPILER_MINGW) && defined(PTW32_VERSION)
+	struct pthread_cmp
+	{
+		bool operator() (const ptw32_handle_t& thread1, const ptw32_handle_t& thread2)
+		{
+			return thread1.p < thread2.p;
+		}
+	};
+	typedef typename std::map<pthread_t,RequestBuffer*, pthread_cmp>::iterator RequestBufferMapIterator;
+	typedef std::map<pthread_t,RequestBuffer*, pthread_cmp> RequestBufferMap;
+#else
 	typedef typename std::map<pthread_t,RequestBuffer*>::iterator RequestBufferMapIterator;
 	typedef std::map<pthread_t,RequestBuffer*> RequestBufferMap;
+#endif
 
 	RequestBufferMap request_buffers;
         static Glib::Threads::Private<RequestBuffer> per_thread_request_buffer;