diff --git a/dom/base/StyleSheetList.cpp b/dom/base/StyleSheetList.cpp
index e1815c96f003..d96d0b21a4d0 100644
--- a/dom/base/StyleSheetList.cpp
+++ b/dom/base/StyleSheetList.cpp
@@ -34,6 +34,7 @@ void StyleSheetList::NodeWillBeDestroyed(nsINode* aNode) {
 
 StyleSheetList::StyleSheetList(DocumentOrShadowRoot& aScope)
     : mDocumentOrShadowRoot(&aScope) {
+  SetEnabledCallbacks(nsIMutationObserver::kNodeWillBeDestroyed);
   mDocumentOrShadowRoot->AsNode().AddMutationObserver(this);
 }