--- /dev/null
+--TEST--
+Exception for an undefined trait
+--TEMPLATE--
+{% use 'foo' with foobar as bar %}
+--TEMPLATE(foo)--
+{% block bar %}
+{% endblock %}
+--EXCEPTION--
+Twig_Error_Runtime: Block "foobar" is not defined in trait "foo" in "index.twig" at line 2.