--- a/xpcom/threads/TaskQueue.h
+++ b/xpcom/threads/TaskQueue.h
@@ -64,17 +64,21 @@ public:
   void Dispatch(already_AddRefed<nsIRunnable> aRunnable,
                 DispatchFailureHandling aFailureHandling = AssertDispatchSuccess,
                 DispatchReason aReason = NormalDispatch) override
   {
     nsCOMPtr<nsIRunnable> r = aRunnable;
     {
       MonitorAutoLock mon(mQueueMonitor);
       nsresult rv = DispatchLocked(/* passed by ref */r, aFailureHandling, aReason);
-      MOZ_DIAGNOSTIC_ASSERT(aFailureHandling == DontAssertDispatchSuccess || NS_SUCCEEDED(rv));
+#if defined(DEBUG) || !defined(RELEASE_OR_BETA) || defined(EARLY_BETA_OR_EARLIER)
+      if (NS_FAILED(rv) && aFailureHandling == AssertDispatchSuccess) {
+        MOZ_CRASH_UNSAFE_PRINTF("%s: Dispatch failed. rv=%x", mName, uint32_t(rv));
+      }
+#endif
       Unused << rv;
     }
     // If the ownership of |r| is not transferred in DispatchLocked() due to
     // dispatch failure, it will be deleted here outside the lock. We do so
     // since the destructor of the runnable might access TaskQueue and result
     // in deadlocks.
   }