diff --git a/layout/base/nsCSSRendering.cpp b/layout/base/nsCSSRendering.cpp
index 85a84f731d3..741b9428768 100644
--- a/layout/base/nsCSSRendering.cpp
+++ b/layout/base/nsCSSRendering.cpp
@@ -1077,6 +1077,7 @@ nsCSSRendering::PaintBoxShadow(nsPresContext* aPresContext,
                     twipsPerPixel, &borderRadii);
 
   gfxRect frameGfxRect = RectToGfxRect(frameRect, twipsPerPixel);
+  frameGfxRect.Round();
   gfxRect dirtyGfxRect = RectToGfxRect(aDirtyRect, twipsPerPixel);
 
   for (PRUint32 i = styleBorder->mBoxShadow->Length(); i > 0; --i) {
@@ -1087,7 +1088,7 @@ nsCSSRendering::PaintBoxShadow(nsPresContext* aPresContext,
 
     gfxRect shadowRectPlusBlur = shadowRect;
     shadowRect.ScaleInverse(twipsPerPixel);
-    shadowRect.RoundOut();
+    shadowRect.Round();
 
     // shadowRect won't include the blur, so make an extra rect here that includes the blur
     // for use in the even-odd rule below.
diff --git a/layout/reftests/box-shadow/boxshadow-rounding-ref.html b/layout/reftests/box-shadow/boxshadow-rounding-ref.html
new file mode 100644
index 00000000000..1a56d17ae30
--- /dev/null
+++ b/layout/reftests/box-shadow/boxshadow-rounding-ref.html
@@ -0,0 +1 @@
+<div style="width: 100px; height: 200px; -moz-box-shadow: 3px 3px 2px black; background-color: green;">Hello</div>
diff --git a/layout/reftests/box-shadow/boxshadow-rounding.html b/layout/reftests/box-shadow/boxshadow-rounding.html
new file mode 100644
index 00000000000..4325163d936
--- /dev/null
+++ b/layout/reftests/box-shadow/boxshadow-rounding.html
@@ -0,0 +1 @@
+<div style="width: 100.2px; height: 200.2px; -moz-box-shadow: 3px 3px 2px black; background-color: green;">Hello</div>
diff --git a/layout/reftests/box-shadow/reftest.list b/layout/reftests/box-shadow/reftest.list
index e486887dc28..bcb978fe69a 100644
--- a/layout/reftests/box-shadow/reftest.list
+++ b/layout/reftests/box-shadow/reftest.list
@@ -5,3 +5,4 @@
 == tableboxshadow-basic.html tableboxshadow-basic-ref.html
 == tableboxshadow-trshadow.html tableboxshadow-trshadow-ref.html
 == tableboxshadow-tdshadow.html tableboxshadow-tdshadow-ref.html
+== boxshadow-rounding.html boxshadow-rounding-ref.html