--- a/editor/libeditor/EditorBase.cpp
+++ b/editor/libeditor/EditorBase.cpp
@@ -554,22 +554,28 @@ EditorBase::IsSelectionEditable()
 
   if (!mIsHTMLEditorClass) {
     // XXX we just check that the anchor node is editable at the moment
     //     we should check that all nodes in the selection are editable
     nsCOMPtr<nsINode> anchorNode = selection->GetAnchorNode();
     return anchorNode && IsEditable(anchorNode);
   }
 
+  nsINode* anchorNode = selection->GetAnchorNode();
+  nsINode* focusNode = selection->GetFocusNode();
+  if (!anchorNode || !focusNode) {
+    return false;
+  }
+
   // Per the editing spec as of June 2012: we have to have a selection whose
   // start and end nodes are editable, and which share an ancestor editing
   // host.  (Bug 766387.)
   bool isSelectionEditable = selection->RangeCount() &&
-                             selection->GetAnchorNode()->IsEditable() &&
-                             selection->GetFocusNode()->IsEditable();
+                             anchorNode->IsEditable() &&
+                             focusNode->IsEditable();
   if (!isSelectionEditable) {
     return false;
   }
 
   nsINode* commonAncestor =
     selection->GetAnchorFocusRange()->GetCommonAncestor();
   while (commonAncestor && !commonAncestor->IsEditable()) {
     commonAncestor = commonAncestor->GetParentNode();