--- a/widget/cocoa/nsNativeThemeCocoa.mm
+++ b/widget/cocoa/nsNativeThemeCocoa.mm
@@ -2699,17 +2699,17 @@ nsNativeThemeCocoa::ComputeScrollbarPara
 {
   ScrollbarParams params;
   params.overlay = nsLookAndFeel::UseOverlayScrollbars();
   params.rolledOver = IsParentScrollbarRolledOver(aFrame);
   nsIFrame* scrollbarFrame = GetParentScrollbarFrame(aFrame);
   params.small =
     (scrollbarFrame &&
      scrollbarFrame->StyleDisplay()->mAppearance == NS_THEME_SCROLLBAR_SMALL);
-  params.rtl = aFrame->StyleVisibility()->mDirection == NS_STYLE_DIRECTION_RTL;
+  params.rtl = IsFrameRTL(aFrame);
   params.horizontal = aIsHorizontal;
   params.onDarkBackground = IsDarkBackground(aFrame);
   return params;
 }
 
 void
 nsNativeThemeCocoa::DrawScrollbarThumb(CGContextRef cgContext,
                                        const CGRect& inBoxRect,