diff --git a/gfx/layers/LayerTreeInvalidation.cpp b/gfx/layers/LayerTreeInvalidation.cpp
index 13319271d2d7..470f29b41838 100644
--- a/gfx/layers/LayerTreeInvalidation.cpp
+++ b/gfx/layers/LayerTreeInvalidation.cpp
@@ -59,12 +59,14 @@ AddTransformedRegion(nsIntRegion& aDest, const nsIntRegion& aSource, const gfx3D
   while ((r = iter.Next())) {
     aDest.Or(aDest, TransformRect(*r, aTransform));
   }
+  aDest.SimplifyOutward(20);
 }
 
 static void
 AddRegion(nsIntRegion& aDest, const nsIntRegion& aSource)
 {
   aDest.Or(aDest, aSource);
+  aDest.SimplifyOutward(20);
 }
 
 static nsIntRegion
diff --git a/gfx/layers/basic/BasicThebesLayer.h b/gfx/layers/basic/BasicThebesLayer.h
index c84060aa8925..5af62dc67c77 100644
--- a/gfx/layers/basic/BasicThebesLayer.h
+++ b/gfx/layers/basic/BasicThebesLayer.h
@@ -53,6 +53,7 @@ public:
     NS_ASSERTION(BasicManager()->InConstruction(),
                  "Can only set properties in construction phase");
     mInvalidRegion.Or(mInvalidRegion, aRegion);
+    mInvalidRegion.SimplifyOutward(20);
     mValidRegion.Sub(mValidRegion, mInvalidRegion);
   }
 
diff --git a/gfx/layers/client/ClientThebesLayer.h b/gfx/layers/client/ClientThebesLayer.h
index 7ee9b9c4c8cf..098013167ac6 100644
--- a/gfx/layers/client/ClientThebesLayer.h
+++ b/gfx/layers/client/ClientThebesLayer.h
@@ -60,6 +60,7 @@ public:
     NS_ASSERTION(ClientManager()->InConstruction(),
                  "Can only set properties in construction phase");
     mInvalidRegion.Or(mInvalidRegion, aRegion);
+    mInvalidRegion.SimplifyOutward(20);
     mValidRegion.Sub(mValidRegion, mInvalidRegion);
   }
 
diff --git a/gfx/layers/d3d10/ThebesLayerD3D10.cpp b/gfx/layers/d3d10/ThebesLayerD3D10.cpp
index 6fabe8678eda..976aae3b842a 100644
--- a/gfx/layers/d3d10/ThebesLayerD3D10.cpp
+++ b/gfx/layers/d3d10/ThebesLayerD3D10.cpp
@@ -47,7 +47,7 @@ void
 ThebesLayerD3D10::InvalidateRegion(const nsIntRegion &aRegion)
 {
   mInvalidRegion.Or(mInvalidRegion, aRegion);
-  mInvalidRegion.SimplifyOutward(10);
+  mInvalidRegion.SimplifyOutward(20);
   mValidRegion.Sub(mValidRegion, mInvalidRegion);
 }
 
diff --git a/gfx/layers/d3d9/ThebesLayerD3D9.cpp b/gfx/layers/d3d9/ThebesLayerD3D9.cpp
index 500aa9cd4c6e..f692a158b5bc 100644
--- a/gfx/layers/d3d9/ThebesLayerD3D9.cpp
+++ b/gfx/layers/d3d9/ThebesLayerD3D9.cpp
@@ -50,6 +50,7 @@ void
 ThebesLayerD3D9::InvalidateRegion(const nsIntRegion &aRegion)
 {
   mInvalidRegion.Or(mInvalidRegion, aRegion);
+  mInvalidRegion.SimplifyOutward(20);
   mValidRegion.Sub(mValidRegion, mInvalidRegion);
 }