--- a/dom/base/Selection.h
+++ b/dom/base/Selection.h
@@ -432,17 +432,17 @@ private:
   // us to perform binary searches when searching for existence of a range,
   // giving us O(log n) search time.
   //
   // Inserting a new range requires finding the overlapping interval, requiring
   // two binary searches plus up to an additional 6 DOM comparisons. If this
   // proves to be a performance concern, then an interval tree may be a
   // possible solution, allowing the calculation of the overlap interval in
   // O(log n) time, though this would require rebalancing and other overhead.
-  nsTArray<RangeData> mRanges;
+  AutoTArray<RangeData, 1> mRanges;
 
   RefPtr<nsRange> mAnchorFocusRange;
   RefPtr<nsFrameSelection> mFrameSelection;
   RefPtr<nsAutoScrollTimer> mAutoScrollTimer;
   FallibleTArray<nsCOMPtr<nsISelectionListener>> mSelectionListeners;
   nsRevocableEventPtr<ScrollSelectionIntoViewEvent> mScrollEvent;
   CachedOffsetForFrame* mCachedOffsetForFrame;
   nsDirection mDirection;