diff --git a/widget/src/cocoa/nsChildView.mm b/widget/src/cocoa/nsChildView.mm
index 0cb72eba43af..8a45fd72767b 100644
--- a/widget/src/cocoa/nsChildView.mm
+++ b/widget/src/cocoa/nsChildView.mm
@@ -2002,7 +2002,7 @@ nsChildView::Idle()
   
 } // mouseUp
 
-const PRInt32 kNumLines = 8;
+const PRInt32 kNumLines = 4;
 
 -(void)scrollWheel:(NSEvent*)theEvent
 {