diff --git a/dom/xbl/nsXBLBinding.cpp b/dom/xbl/nsXBLBinding.cpp
index 07452f89fbe0..26953d4e008b 100644
--- a/dom/xbl/nsXBLBinding.cpp
+++ b/dom/xbl/nsXBLBinding.cpp
@@ -869,7 +869,7 @@ nsXBLBinding::WalkRules(nsIStyleRuleProcessor::EnumFunc aFunc, void* aData)
     (*aFunc)(rules, aData);
 }
 
-const ServoStyleSet*
+ServoStyleSet*
 nsXBLBinding::GetServoStyleSet() const
 {
   return mPrototypeBinding->GetServoStyleSet();
diff --git a/dom/xbl/nsXBLBinding.h b/dom/xbl/nsXBLBinding.h
index 5cdbdf8c1562..c9bb5ddb4454 100644
--- a/dom/xbl/nsXBLBinding.h
+++ b/dom/xbl/nsXBLBinding.h
@@ -130,7 +130,7 @@ public:
 
   void WalkRules(nsIStyleRuleProcessor::EnumFunc aFunc, void* aData);
 
-  const mozilla::ServoStyleSet* GetServoStyleSet() const;
+  mozilla::ServoStyleSet* GetServoStyleSet() const;
 
   static nsresult DoInitJSClass(JSContext *cx, JS::Handle<JSObject*> obj,
                                 const nsString& aClassName,
diff --git a/dom/xbl/nsXBLPrototypeBinding.cpp b/dom/xbl/nsXBLPrototypeBinding.cpp
index 5616da797fbb..6f23bcddaf70 100644
--- a/dom/xbl/nsXBLPrototypeBinding.cpp
+++ b/dom/xbl/nsXBLPrototypeBinding.cpp
@@ -569,7 +569,7 @@ nsXBLPrototypeBinding::GetRuleProcessor()
   return nullptr;
 }
 
-const ServoStyleSet*
+ServoStyleSet*
 nsXBLPrototypeBinding::GetServoStyleSet() const
 {
   return mResources ? mResources->GetServoStyleSet() : nullptr;
diff --git a/dom/xbl/nsXBLPrototypeBinding.h b/dom/xbl/nsXBLPrototypeBinding.h
index 964ffad235ee..81765f539239 100644
--- a/dom/xbl/nsXBLPrototypeBinding.h
+++ b/dom/xbl/nsXBLPrototypeBinding.h
@@ -131,7 +131,7 @@ public:
   void AppendStyleSheetsTo(nsTArray<mozilla::StyleSheet*>& aResult) const;
 
   nsIStyleRuleProcessor* GetRuleProcessor();
-  const mozilla::ServoStyleSet* GetServoStyleSet() const;
+  mozilla::ServoStyleSet* GetServoStyleSet() const;
 
   nsresult FlushSkinSheets();
 
diff --git a/dom/xbl/nsXBLPrototypeResources.h b/dom/xbl/nsXBLPrototypeResources.h
index 721252f349fc..05cab60097bc 100644
--- a/dom/xbl/nsXBLPrototypeResources.h
+++ b/dom/xbl/nsXBLPrototypeResources.h
@@ -64,7 +64,7 @@ public:
   // the Servo style backend.
   void ComputeServoStyleSet(nsPresContext* aPresContext);
 
-  const mozilla::ServoStyleSet* GetServoStyleSet() const { return mServoStyleSet.get(); }
+  mozilla::ServoStyleSet* GetServoStyleSet() const { return mServoStyleSet.get(); }
 
 private:
   // A loader object. Exists only long enough to load resources, and then it dies.