--- a/layout/base/AccessibleCaretManager.cpp
+++ b/layout/base/AccessibleCaretManager.cpp
@@ -1027,16 +1027,19 @@ AccessibleCaretManager::RestrictCaretDra
   nsIFrame* frame =
     GetFrameForFirstRangeStartOrLastRangeEnd(dir, &offset, &node, &contentOffset);
 
   if (!frame) {
     return false;
   }
 
   nsCOMPtr<nsIContent> content = do_QueryInterface(node);
+  if (!content) {
+    return false;
+  }
 
   // Compare the active caret's new position (aOffsets) to the inactive caret's
   // position.
   int32_t cmpToInactiveCaretPos =
     nsContentUtils::ComparePoints(aOffsets.content, aOffsets.StartOffset(),
                                   content, contentOffset);
 
   // Move one character (in the direction of dir) from the inactive caret's