--- a/layout/base/AccessibleCaretManager.cpp
+++ b/layout/base/AccessibleCaretManager.cpp
@@ -801,17 +801,20 @@ AccessibleCaretManager::GetFrameSelectio
     return mPresShell->FrameSelection();
   }
 }
 
 nsAutoString
 AccessibleCaretManager::StringifiedSelection() const
 {
   nsAutoString str;
-  GetSelection()->Stringify(str);
+  Selection* selection = GetSelection();
+  if (selection) {
+    selection->Stringify(str);
+  }
   return str;
 }
 
 Element*
 AccessibleCaretManager::GetEditingHostForFrame(nsIFrame* aFrame) const
 {
   if (!aFrame) {
     return nullptr;