--- a/gfx/layers/apz/src/APZCTreeManager.cpp
+++ b/gfx/layers/apz/src/APZCTreeManager.cpp
@@ -2183,24 +2183,22 @@ APZCTreeManager::GetTargetNode(const Scr
   return target.forget();
 }
 
 already_AddRefed<AsyncPanZoomController>
 APZCTreeManager::GetTargetAPZC(const ScreenPoint& aPoint,
                                HitTestResult* aOutHitResult,
                                RefPtr<HitTestingTreeNode>* aOutScrollbarNode)
 {
+  MutexAutoLock lock(mTreeLock);
+
   HitTestResult hitResult = HitNothing;
   HitTestingTreeNode* scrollbarNode = nullptr;
   RefPtr<AsyncPanZoomController> target;
-
-  { // scope mTreeLock
-    MutexAutoLock lock(mTreeLock);
-    target = GetAPZCAtPoint(mRootNode, aPoint, &hitResult, &scrollbarNode);
-  }
+  target = GetAPZCAtPoint(mRootNode, aPoint, &hitResult, &scrollbarNode);
 
   if (gfxPrefs::WebRenderHitTest()) {
     HitTestResult wrHitResult = HitNothing;
     RefPtr<AsyncPanZoomController> wrTarget = GetAPZCAtPointWR(aPoint, &wrHitResult);
     // For now just compare the WR and non-WR results.
     if (wrHitResult != hitResult) {
       printf_stderr("WR hit result mismatch at %s: got %d, expected %d\n",
           Stringify(aPoint).c_str(), (int)wrHitResult, (int)hitResult);
@@ -2241,17 +2239,21 @@ APZCTreeManager::GetAPZCAtPointWR(const 
   gfx::CompositorHitTestInfo hitInfo;
   bool hitSomething = wr->HitTest(wr::ToWorldPoint(aHitTestPoint),
       pipelineId, scrollId, hitInfo);
   if (!hitSomething) {
     return result.forget();
   }
 
   uint64_t layersId = wr::AsUint64(pipelineId);
-  result = GetTargetAPZC(layersId, scrollId);
+  RefPtr<HitTestingTreeNode> node = GetTargetNode(
+      ScrollableLayerGuid(layersId, 0, scrollId),
+      &GuidComparatorIgnoringPresShell);
+  MOZ_ASSERT(!node || node->GetApzc()); // any node returned must have an APZC
+  result = node ? node->GetApzc() : nullptr;
   if (!result) {
     // It falls back to the root
     MOZ_ASSERT(scrollId == FrameMetrics::NULL_SCROLL_ID);
     result = FindRootApzcForLayersId(layersId);
     MOZ_ASSERT(result);
   }
 
   *aOutHitResult = HitLayer;