diff --git a/mozilla/widget/timer/public/nsITimer.h b/mozilla/widget/timer/public/nsITimer.h
index 40f53142b6d..16fadd5bcad 100644
--- a/mozilla/widget/timer/public/nsITimer.h
+++ b/mozilla/widget/timer/public/nsITimer.h
@@ -69,7 +69,7 @@ typedef void
                                      // sucession.
 
 // --- Indicate if timers on your platform support repeating timers ---
-#if defined(XP_PC) || defined(XP_UNIX)
+#if defined(XP_PC) || defined(XP_UNIX) || defined(XP_MAC)
 #define REPEATING_TIMERS 1
 #endif