diff --git a/dom/base/FragmentOrElement.cpp b/dom/base/FragmentOrElement.cpp
index 22039babef4a..13a3ea6ae326 100644
--- a/dom/base/FragmentOrElement.cpp
+++ b/dom/base/FragmentOrElement.cpp
@@ -1400,6 +1400,13 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(FragmentOrElement)
   {
     nsDOMSlots *slots = tmp->GetExistingDOMSlots();
     if (slots) {
+      if (tmp->IsElement()) {
+        Element* elem = tmp->AsElement();
+        for (auto iter = slots->mRegisteredIntersectionObservers.Iter(); !iter.Done(); iter.Next()) {
+          DOMIntersectionObserver* observer = iter.Key();
+          observer->UnlinkTarget(*elem);
+        }
+      }
       slots->Unlink(tmp->IsXULElement());
     }
   }
diff --git a/dom/base/nsNodeUtils.cpp b/dom/base/nsNodeUtils.cpp
index 5eda61e9b38b..d1c7c288e4c2 100644
--- a/dom/base/nsNodeUtils.cpp
+++ b/dom/base/nsNodeUtils.cpp
@@ -297,16 +297,6 @@ nsNodeUtils::LastRelease(nsINode* aNode)
                                          NodeWillBeDestroyed, (aNode));
     }
 
-    if (aNode->IsElement()) {
-      Element* elem = aNode->AsElement();
-      FragmentOrElement::nsDOMSlots* domSlots =
-        static_cast<FragmentOrElement::nsDOMSlots*>(slots);
-      for (auto iter = domSlots->mRegisteredIntersectionObservers.Iter(); !iter.Done(); iter.Next()) {
-        DOMIntersectionObserver* observer = iter.Key();
-        observer->UnlinkTarget(*elem);
-      }
-    }
-
     delete slots;
     aNode->mSlots = nullptr;
   }