--- a/dom/base/ScriptSettings.cpp
+++ b/dom/base/ScriptSettings.cpp
@@ -132,17 +132,17 @@ nsIDocument*
 GetEntryDocument()
 {
   nsIGlobalObject* global = GetEntryGlobal();
   nsCOMPtr<nsPIDOMWindow> entryWin = do_QueryInterface(global);
 
   // If our entry global isn't a window, see if it's an addon scope associated
   // with a window. If it is, the caller almost certainly wants that rather
   // than null.
-  if (!entryWin) {
+  if (!entryWin && global) {
     entryWin = xpc::AddonWindowOrNull(global->GetGlobalJSObject());
   }
 
   return entryWin ? entryWin->GetExtantDoc() : nullptr;
 }
 
 nsIGlobalObject*
 GetIncumbentGlobal()