--- a/gfx/layers/apz/src/AsyncPanZoomController.cpp
+++ b/gfx/layers/apz/src/AsyncPanZoomController.cpp
@@ -903,16 +903,20 @@ nsEventStatus AsyncPanZoomController::Ha
 
   if (aEvent.mType != MouseInput::MouseType::MOUSE_MOVE) {
     return nsEventStatus_eConsumeNoDefault;
   }
 
   RefPtr<HitTestingTreeNode> node =
     GetApzcTreeManager()->FindScrollThumbNode(aDragMetrics);
   if (!node) {
+    // One possible reason why we couldn't find the scroll thumb node is that
+    // the page content has changed from under us. In such a case, request a
+    // repaint to make sure the new page content is shown.
+    ScheduleCompositeAndMaybeRepaint();
     return nsEventStatus_eConsumeNoDefault;
   }
 
   const ScrollThumbData& thumbData = node->GetScrollThumbData();
 
   mozilla::Telemetry::Accumulate(mozilla::Telemetry::SCROLL_INPUT_METHODS,
       (uint32_t) ScrollInputMethod::ApzScrollbarDrag);