--- a/dom/base/nsDOMWindowUtils.cpp
+++ b/dom/base/nsDOMWindowUtils.cpp
@@ -2595,16 +2595,17 @@ nsDOMWindowUtils::FlushApzRepaints(bool*
     return NS_OK;
   }
   if (WebRenderLayerManager* wrlm = manager->AsWebRenderLayerManager()) {
     WebRenderBridgeChild* wrbc = wrlm->WrBridge();
     if (!wrbc) {
       return NS_ERROR_UNEXPECTED;
     }
     wrbc->SendFlushApzRepaints();
+    *aOutResult = true;
     return NS_OK;
   }
   ShadowLayerForwarder* forwarder = manager->AsShadowForwarder();
   if (!forwarder || !forwarder->HasShadowManager()) {
     *aOutResult = false;
     return NS_OK;
   }
   forwarder->GetShadowManager()->SendFlushApzRepaints();