diff --git a/dom/base/RadioGroupContainer.cpp b/dom/base/RadioGroupContainer.cpp
index 988c8186f983..650d03a56d24 100644
--- a/dom/base/RadioGroupContainer.cpp
+++ b/dom/base/RadioGroupContainer.cpp
@@ -65,7 +65,7 @@ void RadioGroupContainer::Traverse(RadioGroupContainer* tmp,
 
 size_t RadioGroupContainer::SizeOfIncludingThis(
     MallocSizeOf aMallocSizeOf) const {
-  return mRadioGroups.SizeOfIncludingThis(aMallocSizeOf);
+  return aMallocSizeOf(this) + mRadioGroups.SizeOfExcludingThis(aMallocSizeOf);
 }
 
 nsresult RadioGroupContainer::WalkRadioGroup(const nsAString& aName,
diff --git a/dom/base/RadioGroupContainer.h b/dom/base/RadioGroupContainer.h
index 6331c71dd9b6..c6eea23bb2da 100644
--- a/dom/base/RadioGroupContainer.h
+++ b/dom/base/RadioGroupContainer.h
@@ -26,7 +26,7 @@ class RadioGroupContainer final {
                        nsCycleCollectionTraversalCallback& cb);
   size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const;
 
-  NS_IMETHOD WalkRadioGroup(const nsAString& aName, nsIRadioVisitor* aVisitor);
+  nsresult WalkRadioGroup(const nsAString& aName, nsIRadioVisitor* aVisitor);
   void SetCurrentRadioButton(const nsAString& aName, HTMLInputElement* aRadio);
   HTMLInputElement* GetCurrentRadioButton(const nsAString& aName);
   nsresult GetNextRadioButton(const nsAString& aName, const bool aPrevious,