--- a/layout/style/nsCSSRules.h
+++ b/layout/style/nsCSSRules.h
@@ -374,17 +374,17 @@ public:
 
   virtual nsINode* GetParentObject() override;
 
 protected:
   virtual ~nsCSSKeyframeStyleDeclaration();
 
   // This reference is not reference-counted. The rule object tells us
   // when it's about to go away.
-  nsCSSKeyframeRule *mRule;
+  nsCSSKeyframeRule* MOZ_NON_OWNING_REF mRule;
 };
 
 class nsCSSKeyframeRule final : public mozilla::css::Rule,
                                 public nsIDOMMozCSSKeyframeRule
 {
 public:
   // WARNING: Steals the contents of aKeys *and* aDeclaration
   nsCSSKeyframeRule(InfallibleTArray<float>& aKeys,
@@ -507,17 +507,17 @@ public:
 
   virtual nsINode *GetParentObject() override;
 
 protected:
   virtual ~nsCSSPageStyleDeclaration();
 
   // This reference is not reference-counted. The rule object tells us
   // when it's about to go away.
-  nsCSSPageRule *mRule;
+  nsCSSPageRule* MOZ_NON_OWNING_REF mRule;
 };
 
 class nsCSSPageRule final : public mozilla::css::Rule,
                             public nsIDOMCSSPageRule
 {
 public:
   // WARNING: Steals the contents of aDeclaration
   nsCSSPageRule(nsAutoPtr<mozilla::css::Declaration>&& aDeclaration,