diff --git a/dom/base/nsCopySupport.cpp b/dom/base/nsCopySupport.cpp
index 60a94d9884..9517a30fa6 100644
--- a/dom/base/nsCopySupport.cpp
+++ b/dom/base/nsCopySupport.cpp
@@ -298,6 +298,8 @@ nsCopySupport::GetTransferableForNode(nsINode* aNode,
 {
   nsCOMPtr<nsISelection> selection;
   // Make a temporary selection with aNode in a single range.
+  // XXX For better performance, we should try to get rid of the
+  // Selection object here. See BMO bug 1245883
   nsresult rv = NS_NewDomSelection(getter_AddRefs(selection));
   NS_ENSURE_SUCCESS(rv, rv);
   nsCOMPtr<nsIDOMNode> node = do_QueryInterface(aNode);
@@ -305,7 +307,9 @@ nsCopySupport::GetTransferableForNode(nsINode* aNode,
   nsRefPtr<nsRange> range = new nsRange(aNode);
   rv = range->SelectNode(node);
   NS_ENSURE_SUCCESS(rv, rv);
-  rv = selection->AddRange(range);
+  ErrorResult result;
+  selection->AsSelection()->AddRangeInternal(*range, aDoc, result);
+  rv = result.StealNSResult();
   NS_ENSURE_SUCCESS(rv, rv);
   // It's not the primary selection - so don't skip invisible content.
   uint32_t flags = 0;
diff --git a/dom/base/nsDocumentEncoder.cpp b/dom/base/nsDocumentEncoder.cpp
index 3471ebac36..7ea49009b4 100644
--- a/dom/base/nsDocumentEncoder.cpp
+++ b/dom/base/nsDocumentEncoder.cpp
@@ -1396,6 +1396,9 @@ nsHTMLCopyEncoder::SetSelection(nsISelection* aSelection)
   }
 #endif
 
+  // XXX For better performance, we should try to get rid of the
+  // Selection object here. See BMO bug 1245883
+  
   // also consider ourselves in a text widget if we can't find an html document
   nsCOMPtr<nsIHTMLDocument> htmlDoc = do_QueryInterface(mDocument);
   if (!(htmlDoc && mDocument->IsHTML())) {
@@ -1423,7 +1426,10 @@ nsHTMLCopyEncoder::SetSelection(nsISelection* aSelection)
     rv = PromoteRange(myRange);
     NS_ENSURE_SUCCESS(rv, rv);
     
-    rv = mSelection->AddRange(myRange);
+    ErrorResult result;
+    nsRange* r = static_cast<nsRange*>(myRange.get());
+    mSelection->AsSelection()->AddRangeInternal(*r, mDocument, result);
+    rv = result.StealNSResult();
     NS_ENSURE_SUCCESS(rv, rv);
   }
 
diff --git a/layout/generic/Selection.h b/layout/generic/Selection.h
index 875bc01e20..14ad1e78ef 100644
--- a/layout/generic/Selection.h
+++ b/layout/generic/Selection.h
@@ -24,6 +24,8 @@ class nsIContentIterator;
 class nsIFrame;
 class nsFrameSelection;
 struct SelectionDetails;
+class nsCopySupport;
+class nsHTMLCopyEncoder;
 
 namespace mozilla {
 class ErrorResult;
@@ -209,6 +211,12 @@ private:
   // Note: DoAutoScroll might destroy arbitrary frames etc.
   nsresult DoAutoScroll(nsIFrame *aFrame, nsPoint& aPoint);
 
+  // XXX Please don't add additional uses of this method; it's only for
+  // XXX supporting broken code (BMO bug 1245883) in the following classes:
+  friend class ::nsCopySupport;
+  friend class ::nsHTMLCopyEncoder;
+  void AddRangeInternal(nsRange& aRange, nsIDocument* aDocument, ErrorResult&);
+
 public:
   SelectionType GetType(){return mType;}
   void          SetType(SelectionType aType){mType = aType;}
diff --git a/layout/generic/nsSelection.cpp b/layout/generic/nsSelection.cpp
index 6d1808df6e..fb8fcd66a5 100644
--- a/layout/generic/nsSelection.cpp
+++ b/layout/generic/nsSelection.cpp
@@ -4632,6 +4632,22 @@ Selection::AddRange(nsIDOMRange* aDOMRange)
 void
 Selection::AddRange(nsRange& aRange, ErrorResult& aRv)
 {
+  return AddRangeInternal(aRange, GetParentObject(), aRv);
+}
+
+void
+Selection::AddRangeInternal(nsRange& aRange, nsIDocument* aDocument,
+                            ErrorResult& aRv)
+{
+  nsINode* rangeRoot = aRange.GetRoot();
+  if (aDocument != rangeRoot && (!rangeRoot ||
+                                 aDocument != rangeRoot->GetComposedDoc())) {
+    // http://w3c.github.io/selection-api/#dom-selection-addrange
+    // "...  if the root of the range's boundary points are the document
+    // associated with context object. Otherwise, this method must do nothing."
+    return;
+  }
+
   // This inserts a table cell range in proper document order
   // and returns NS_OK if range doesn't contain just one table cell
   bool didAddRange;