diff --git a/common/modules/commands.jsm b/common/modules/commands.jsm
index 67c82ac1..f1929297 100644
--- a/common/modules/commands.jsm
+++ b/common/modules/commands.jsm
@@ -331,8 +331,9 @@ var Command = Class("Command", {
     }),
 
     newArgs: function newArgs(base) {
-        let res = Object.create(this.argsPrototype);
+        let res = [];
         update(res, base);
+        res.__proto__ = this.argsPrototype;
         return res;
     },