There is a typo in 11.3.26

http://docs.jboss.org/cdi/spec/1.1/cdi-spec.html#bm_obtain_extension

The method BeanManager.getExtensions() returns the container’s instance of an Extension class

Should be: The method `BeanManager.getExtension(Class<? extends Extension> clazz)`

This matches API docs and the verbiage at the end of the spec.