Wurdearring: 3 fan de 5 stjerren

Cleaning the subject of an email with the following subject line when I forward it doesn't work properly:
RE: [Fwd: RE: Subject]
It results in a new subject line of just:
Re:
How do I fix that? Note, that using Reply on this email works fine.
David.

Dizze beoardieling giet oer in eardere ferzje fan de add-on (0.4.1).