diff --git a/is-native-implemented.js b/is-native-implemented.js
index <HASH>..<HASH> 100644
--- a/is-native-implemented.js
+++ b/is-native-implemented.js
@@ -1,10 +1,8 @@
-// Exports true if environment provides native `WeakMap` implementation,
-// whatever that is.
+// Exports true if environment provides native `WeakMap` implementation, whatever that is.
 
 'use strict';
 
 module.exports = (function () {
-	if (typeof WeakMap === 'undefined') return false;
-	return (Object.prototype.toString.call(WeakMap.prototype) ===
-			'[object WeakMap]');
+	if (typeof WeakMap !== 'function') return false;
+	return (Object.prototype.toString.call(new WeakMap()) === '[object WeakMap]');
 }());
Fix native detection

So it's not affected by V8 bug:
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