--- a/dom/animation/EffectSet.cpp
+++ b/dom/animation/EffectSet.cpp
@@ -34,17 +34,17 @@ EffectSet::Traverse(nsCycleCollectionTra
 {
   for (auto iter = mEffects.Iter(); !iter.Done(); iter.Next()) {
     CycleCollectionNoteChild(aCallback, iter.Get()->GetKey(),
                              "EffectSet::mEffects[]", aCallback.Flags());
   }
 }
 
 /* static */ EffectSet*
-EffectSet::GetEffectSet(dom::Element* aElement,
+EffectSet::GetEffectSet(const dom::Element* aElement,
                         CSSPseudoElementType aPseudoType)
 {
   nsIAtom* propName = GetEffectSetPropertyAtom(aPseudoType);
   return static_cast<EffectSet*>(aElement->GetProperty(propName));
 }
 
 /* static */ EffectSet*
 EffectSet::GetEffectSet(const nsIFrame* aFrame)

--- a/dom/animation/EffectSet.h
+++ b/dom/animation/EffectSet.h
@@ -52,17 +52,17 @@ public:
     MOZ_COUNT_DTOR(EffectSet);
   }
   static void PropertyDtor(void* aObject, nsIAtom* aPropertyName,
                            void* aPropertyValue, void* aData);
 
   // Methods for supporting cycle-collection
   void Traverse(nsCycleCollectionTraversalCallback& aCallback);
 
-  static EffectSet* GetEffectSet(dom::Element* aElement,
+  static EffectSet* GetEffectSet(const dom::Element* aElement,
                                  CSSPseudoElementType aPseudoType);
   static EffectSet* GetEffectSet(const nsIFrame* aFrame);
   static EffectSet* GetOrCreateEffectSet(dom::Element* aElement,
                                          CSSPseudoElementType aPseudoType);
   static void DestroyEffectSet(dom::Element* aElement,
                                CSSPseudoElementType aPseudoType);
 
   void AddEffect(dom::KeyframeEffectReadOnly& aEffect);