Formatter - indent after enter

Hallo,
I have a problem with the indent of the cursor after pressing enter in my custom language. It works as long as the FormattingModelBuilder is not included:

DEFINITION {
     A_REFERENCE
     |(cursor is here)
}

However, when I include my FormattingModelBuilder, the following:

DEFINITION {
     A_REFERENCE
|(cursor is here)
}

After formatting A_REFERENCE is indented correctly. No other elements are allowed in the braces. Is the FormattingModel and the blocks responsible for indenting the cursor or do I have to additionally implement an EnterHandler?

Thanks for any help,
Sebastian