hasOwnProperty is returning false for class properties that were not explicitly set after creating an instance. Example: package { class E { public var a:Number; } (function () { var e = new E(); trace('New instance of "E" has own property "a": ' + e.hasOwnProperty('a')); })(); } This behavior is different to JavaScript, where hasOwnProperty('a') should only return true if the property was set on the instance itself and not just being defined somewhere on the prototype chain.

Fixed in https://github.com/mozilla/shumway/pull/1999