Is there a length limit on the label field in the buttons.cfg file?

I have several buttons that I have first and last name defined on but they are only showing up on the button as their first name. For example I have this button defined:

[SIP/649EF3767278]
type=extension
context=Internal
extension=4883
label=Mitchell Johnson
group=Employer Services

and the button just shows "4883 Mitchell"

The only thing that all the buttons that are acting like this have in common, is long names.