diff --git a/layout/base/FrameLayerBuilder.cpp b/layout/base/FrameLayerBuilder.cpp
index ff4661e1c8..aa49c74cee 100644
--- a/layout/base/FrameLayerBuilder.cpp
+++ b/layout/base/FrameLayerBuilder.cpp
@@ -162,12 +162,7 @@ void
 FrameLayerBuilder::DisplayItemData::AddFrame(nsIFrame* aFrame)
 {
   MOZ_RELEASE_ASSERT(mLayer);
-  
-  // Make sure we don't add duplicate frames as we're storing these as vectors.
-  // See UXP Issue #1860
-  if (!mFrameList.Contains(aFrame)) {
-    mFrameList.AppendElement(aFrame);
-  }
+  mFrameList.AppendElement(aFrame);
 
   nsTArray<DisplayItemData*>* array =
     aFrame->GetProperty(FrameLayerBuilder::LayerManagerDataProperty());