diff --git a/layout/xul/base/src/tree/src/nsTreeColFrame.cpp b/layout/xul/base/src/tree/src/nsTreeColFrame.cpp
index be4823972aa1..8f8f26baeafa 100644
--- a/layout/xul/base/src/tree/src/nsTreeColFrame.cpp
+++ b/layout/xul/base/src/tree/src/nsTreeColFrame.cpp
@@ -123,13 +123,13 @@ nsDisplayXULTreeColSplitterTarget::HitTest(nsDisplayListBuilder* aBuilder,
                                            nsPoint aPt)
 {
   nsPoint pt = aPt - aBuilder->ToReferenceFrame(mFrame);
-  // If we are in either the first 2 pixels or the last 2 pixels, we're going to
+  // If we are in either the first 4 pixels or the last 4 pixels, we're going to
   // do something really strange.  Check for an adjacent splitter.
   PRBool left = PR_FALSE;
   PRBool right = PR_FALSE;
-  if (mFrame->GetSize().width - 60 < pt.x)
+  if (mFrame->GetSize().width - nsPresContext::CSSPixelsToAppUnits(4) <= pt.x)
     right = PR_TRUE;
-  else if (60 > pt.x)
+  else if (nsPresContext::CSSPixelsToAppUnits(4) > pt.x)
     left = PR_TRUE;
 
   if (left || right) {