WELD-SE not running with SE 5

using weld-se with SE 5 dont't work. We found out that classes uses methods that aren't declared in JDK 5 but in JDK 6.
E.G. weld-se (1.1.2.Final) org.jboss.weld.xml.BeansXmlHandler.getContainer() calls String.isEmpty().
Hence, the initialization of the container via 'WeldContainer weld = new Weld().initialize()' failed .