Regression: Asynchronous components (hst:async) is broken

To reproduce:

• Set the property hst:async to true on a hst:containercomponent with components
• Visit the affected page
  Expected result: The components are loaded asynchronously
  Actual result: The components are not loaded.

There is a javascipt error:
Uncaught ReferenceError: b1146050931 is not defined.

This is in the end of the page source:
<script type="text/javascript">b1146050931.c1146050931.AsyncPage.load();</script>
</body>
</html>