Differences in "Delivered-To" header between deliver and LMTP

Hi, I'm transitioning my server over from using the deliver LDA and LMTP.
Suddenly a bunch of sieve filters stopped working, and I noticed the contents of the Delivered-To header are different.

Using Dovecot's deliver LDA, the contents are a bare email address (foo@bar.com). Using Dovecot LMTP, they are in brackets (foo@bar.com). Is there a reason why this isn't consistent between the two delivery agents? It seems like it ought to be.

Jeff