<p dir="auto">File a bug.<br>
This problem is caused in Firefox version 20.<br>
The error is thrown by core.js  in file es6.symbol.js at line<br>
10583:  var D = gOPD(it, key);</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="var $getOwnPropertyDescriptor = function getOwnPropertyDescriptor(it, key) {
  it = toIObject(it);
  key = toPrimitive(key, true);
  if (it === ObjectProto &amp;&amp; has(AllSymbols, key) &amp;&amp; !has(OPSymbols, key)) return;
  var D = gOPD(it, key);
  if (D &amp;&amp; has(AllSymbols, key) &amp;&amp; !(has(it, HIDDEN) &amp;&amp; it[HIDDEN][key])) D.enumerable = true;
  return D;
};"><pre class="notranslate"><code class="notranslate">var $getOwnPropertyDescriptor = function getOwnPropertyDescriptor(it, key) {
  it = toIObject(it);
  key = toPrimitive(key, true);
  if (it === ObjectProto &amp;&amp; has(AllSymbols, key) &amp;&amp; !has(OPSymbols, key)) return;
  var D = gOPD(it, key);
  if (D &amp;&amp; has(AllSymbols, key) &amp;&amp; !(has(it, HIDDEN) &amp;&amp; it[HIDDEN][key])) D.enumerable = true;
  return D;
};
</code></pre></div>
<p dir="auto">This is a blocking issue.</p>
<p dir="auto">Same as <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="185856677" data-permission-text="Title is private" data-url="https://github.com/zloirock/core-js/issues/254" data-hovercard-type="issue" data-hovercard-url="/zloirock/core-js/issues/254/hovercard" href="https://github.com/zloirock/core-js/issues/254">#254</a><br>
firefox version 20</p>