--- a/gfx/layers/ipc/CompositorBridgeParent.cpp
+++ b/gfx/layers/ipc/CompositorBridgeParent.cpp
@@ -1655,17 +1655,19 @@ CompositorBridgeParent::FlushApzRepaints
 {
   MOZ_ASSERT(mApzcTreeManager);
   uint64_t layersId = aLayerTree->GetId();
   if (layersId == 0) {
     // The request is coming from the parent-process layer tree, so we should
     // use the compositor's root layer tree id.
     layersId = mRootLayerTreeID;
   }
-  mApzcTreeManager->FlushApzRepaints(layersId);
+  APZThreadUtils::RunOnControllerThread(NS_NewRunnableFunction([=] () {
+    mApzcTreeManager->FlushApzRepaints(layersId);
+  }));
 }
 
 void
 CompositorBridgeParent::GetAPZTestData(const LayerTransactionParent* aLayerTree,
                                        APZTestData* aOutData)
 {
   MonitorAutoLock lock(*sIndirectLayerTreesLock);
   *aOutData = sIndirectLayerTrees[mRootLayerTreeID].mApzTestData;