diff --git a/src/os_win32.c b/src/os_win32.c
index da48bfd..1adaaed 100644
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -8378,7 +8378,7 @@
  * This function is not expected to fail, but if it does it still returns a
  * valid flag pointer; the flag will remain stuck at zero.
  */
-    const int *
+    volatile int *
 start_timeout(long msec)
 {
     BOOL ret;