diff --git a/contrib/ports/win32/sys_arch.c b/contrib/ports/win32/sys_arch.c
index 2f261dc7..9643ff19 100644
--- a/contrib/ports/win32/sys_arch.c
+++ b/contrib/ports/win32/sys_arch.c
@@ -688,7 +688,7 @@ sys_arch_mbox_tryfetch(sys_mbox_t *q, void **msg)
       *msg  = NULL;
     }
 
-    return SYS_ARCH_TIMEOUT;
+    return SYS_MBOX_EMPTY;
   }
 }