Global messages displayed with <h:messages/> cannot be found in flow-local messages.properties

When a global message (i.e. not field-specific) is added from a validator, the error code must be in a properties file referenced form a MessageSource. If the code is in a flow-local messages.properties it is not found. The Spring Faces validator components on the contrary do find error codes in flow-local messages.properties. This is inconsistent from a developer's point because both messages are displayed from a facelet view that belongs to a specific flow.