diff --git a/test/test.js b/test/test.js
index b845f2a7b..3af460237 100644
--- a/test/test.js
+++ b/test/test.js
@@ -1170,6 +1170,16 @@
 
   /*--------------------------------------------------------------------------*/
 
+  QUnit.module('lodash.isNumber');
+
+  (function() {
+    test('should avoid `[xpconnect wrapped native prototype]` in Firefox', function() {
+      strictEqual(_.isNumber(+"2"), true);
+    });
+  }());
+
+  /*--------------------------------------------------------------------------*/
+
   QUnit.module('lodash.isPlainObject');
 
   (function() {