1 files changed, 18 insertions, 0 deletions
diff --git a/js/src/tests/non262/lexical-environment/unscopables-mutation-frozen.js b/js/src/tests/non262/lexical-environment/unscopables-mutation-frozen.js
new file mode 100644
index 0000000000..632785c05a
--- /dev/null
+++ b/js/src/tests/non262/lexical-environment/unscopables-mutation-frozen.js
@@ -0,0 +1,18 @@
+// When env[@@unscopables].x changes, bindings can appear even if env is inextensible.
+
+let x = "global";
+let unscopables = {x: true};
+let env = Object.create(null);
+env[Symbol.unscopables] = unscopables;
+env.x = "object";
+Object.freeze(env);
+
+for (let i = 0; i < 1004; i++) {
+    if (i === 1000)
+        unscopables.x = false;
+    with (env) {
+        assertEq(x, i < 1000 ? "global" : "object");
+    }
+}
+
+reportCompare(0, 0);