diff --git a/src/org/mozilla/javascript/ScriptRuntime.java b/src/org/mozilla/javascript/ScriptRuntime.java
index a4644ec626..c34e22a4c5 100644
--- a/src/org/mozilla/javascript/ScriptRuntime.java
+++ b/src/org/mozilla/javascript/ScriptRuntime.java
@@ -4267,7 +4267,7 @@ public static void setFunctionProtoAndParent(
             BaseFunction fn, Context cx, Scriptable scope, boolean es6GeneratorFunction) {
         setFunctionProtoAndParent(fn, scope, es6GeneratorFunction);
 
-        if (cx.getLanguageVersion() >= Context.VERSION_ES6) {
+        if (cx != null && cx.getLanguageVersion() >= Context.VERSION_ES6) {
             fn.setStandardPropertyAttributes(ScriptableObject.READONLY | ScriptableObject.DONTENUM);
         }
     }