--- a/dom/base/nsNodeUtils.cpp
+++ b/dom/base/nsNodeUtils.cpp
@@ -565,18 +565,23 @@ nsNodeUtils::CloneAndAdopt(nsINode *aNod
     if (aReparentScope) {
       AutoJSContext cx;
       JS::Rooted<JSObject*> wrapper(cx);
       if ((wrapper = aNode->GetWrapper())) {
         MOZ_ASSERT(IsDOMObject(wrapper));
         JSAutoCompartment ac(cx, wrapper);
         rv = ReparentWrapper(cx, wrapper);
         if (NS_FAILED(rv)) {
+          if (wasRegistered) {
+            aNode->OwnerDoc()->UnregisterActivityObserver(aNode->AsElement());
+          }
           aNode->mNodeInfo.swap(newNodeInfo);
-
+          if (wasRegistered) {
+            aNode->OwnerDoc()->RegisterActivityObserver(aNode->AsElement());
+          }
           return rv;
         }
       }
     }
   }
 
   if (aDeep && (!aClone || !aNode->IsNodeOfType(nsINode::eATTRIBUTE))) {
     // aNode's children.