--- a/layout/style/ServoMediaList.cpp
+++ b/layout/style/ServoMediaList.cpp
@@ -77,14 +77,15 @@ ServoMediaList::Delete(const nsAString& 
     return NS_OK;
   }
   return NS_ERROR_DOM_NOT_FOUND_ERR;
 }
 
 bool
 ServoMediaList::Matches(nsPresContext* aPresContext) const
 {
-  const RawServoStyleSet& rawSet =
+  const RawServoStyleSet* rawSet =
     aPresContext->StyleSet()->AsServo()->RawSet();
-  return Servo_MediaList_Matches(mRawList, &rawSet);
+  MOZ_ASSERT(rawSet, "The RawServoStyleSet should be valid!");
+  return Servo_MediaList_Matches(mRawList, rawSet);
 }
 
 } // namespace mozilla

--- a/layout/style/ServoStyleSet.h
+++ b/layout/style/ServoStyleSet.h
@@ -137,17 +137,19 @@ public:
     return StylistNeedsUpdate();
   }
 
   bool MediumFeaturesChanged() const;
 
   void InvalidateStyleForCSSRuleChanges();
 
   size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
-  const RawServoStyleSet& RawSet() const { return *mRawSet; }
+  const RawServoStyleSet* RawSet() const {
+    return mRawSet.get();
+  }
 
   bool GetAuthorStyleDisabled() const;
   nsresult SetAuthorStyleDisabled(bool aStyleDisabled);
 
   void BeginUpdate();
   nsresult EndUpdate();
 
   already_AddRefed<nsStyleContext>