diff --git a/dom/base/Document.h b/dom/base/Document.h
index 8eccf66133f3..a52c61addffc 100644
--- a/dom/base/Document.h
+++ b/dom/base/Document.h
@@ -3878,7 +3878,12 @@ class Document : public nsINode,
   void SetAllowDeclarativeShadowRoots(bool aAllowDeclarativeShadowRoots);
   bool AllowsDeclarativeShadowRoots() const;
 
-  void SuspendDOMNotifications() { mSuspendDOMNotifications = true; }
+  void SuspendDOMNotifications() {
+    MOZ_ASSERT(IsHTMLDocument(),
+               "Currently suspending DOM notifications is supported only on "
+               "HTML documents.");
+    mSuspendDOMNotifications = true;
+  }
 
   void ResumeDOMNotifications() { mSuspendDOMNotifications = false; }
 
diff --git a/dom/base/MutationObservers.cpp b/dom/base/MutationObservers.cpp
index a4bcdf88d4dd..e3e7c8b02ef9 100644
--- a/dom/base/MutationObservers.cpp
+++ b/dom/base/MutationObservers.cpp
@@ -81,9 +81,6 @@ template <NotifyPresShell aNotifyPresShell = NotifyPresShell::After,
 static inline void Notify(nsINode* aNode, NotifyObserver&& aNotify,
                           uint32_t aCallback) {
   Document* doc = aNode->OwnerDoc();
-  if (doc->DOMNotificationsSuspended()) {
-    return;
-  }
   nsDOMMutationEnterLeave enterLeave(doc);
 
 #ifdef DEBUG
diff --git a/parser/html/nsHtml5TreeOperation.cpp b/parser/html/nsHtml5TreeOperation.cpp
index cb6fda5a5b54..9adfad34bdeb 100644
--- a/parser/html/nsHtml5TreeOperation.cpp
+++ b/parser/html/nsHtml5TreeOperation.cpp
@@ -257,9 +257,10 @@ nsresult nsHtml5TreeOperation::Append(nsIContent* aNode, nsIContent* aParent,
   MOZ_ASSERT(aBuilder);
   MOZ_ASSERT(aBuilder->IsInDocUpdate());
   ErrorResult rv;
-  nsHtml5OtherDocUpdate update(aParent->OwnerDoc(), aBuilder->GetDocument());
+  Document* ownerDoc = aParent->OwnerDoc();
+  nsHtml5OtherDocUpdate update(ownerDoc, aBuilder->GetDocument());
   aParent->AppendChildTo(aNode, false, rv);
-  if (!rv.Failed()) {
+  if (!rv.Failed() && !ownerDoc->DOMNotificationsSuspended()) {
     aNode->SetParserHasNotified();
     MutationObservers::NotifyContentAppended(aParent, aNode);
   }
@@ -303,8 +304,10 @@ nsresult nsHtml5TreeOperation::AppendToDocument(
     return rv.StealNSResult();
   }
 
-  aNode->SetParserHasNotified();
-  MutationObservers::NotifyContentInserted(doc, aNode);
+  if (!doc->DOMNotificationsSuspended()) {
+    aNode->SetParserHasNotified();
+    MutationObservers::NotifyContentInserted(doc, aNode);
+  }
 
   NS_ASSERTION(!nsContentUtils::IsSafeToRunScript(),
                "Someone forgot to block scripts");