diff --git a/test/proto.js b/test/proto.js
new file mode 100644
index 0000000..015ea60
--- /dev/null
+++ b/test/proto.js
@@ -0,0 +1,8 @@
+var parse = require('../');
+var test = require('tape');
+
+test('proto pollution', function (t) {
+    var argv = parse(['--__proto__.x','123']);
+    t.equal({}.x, undefined);
+    t.end();
+});