diff --git a/src/win/win_thread.c b/src/win/win_thread.c
index 1ad0fc469..f97c5a3db 100644
--- a/src/win/win_thread.c
+++ b/src/win/win_thread.c
@@ -45,6 +45,16 @@ thread_create(void (*func)(void *param), void *param)
 }
 
 
+int
+thread_test_mutex(thread_t *arg)
+{
+    if (arg == NULL) return(0);
+
+    return (WaitForSingleObject(arg, 0) == WAIT_OBJECT_0) ? 1 : 0;
+}
+
+
+
 int
 thread_wait(thread_t *arg)
 {