diff --git a/src/os_win32.c b/src/os_win32.c
index 02bcaae..9d36dec 100644
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -1529,15 +1529,19 @@
      */
     for (;;)
     {
+	// Only process messages when waiting.
+	if (msec != 0)
+	{
 #ifdef MESSAGE_QUEUE
-	parse_queued_messages();
+	    parse_queued_messages();
 #endif
 #ifdef FEAT_MZSCHEME
-	mzvim_check_threads();
+	    mzvim_check_threads();
 #endif
 #ifdef FEAT_CLIENTSERVER
-	serverProcessPendingMessages();
+	    serverProcessPendingMessages();
 #endif
+	}
 
 	if (0
 #ifdef FEAT_MOUSE