This appears to have been fixed by commit 89898e43c7ceef28bb3c2116b4d8a3ec96d9c8da in Emacs master.
Subject: Re: notmuch-emacs and Emacs26 (master)
Date: Fri, 21 Apr 2017 17:23:28 -0000
To: aaermolov@gmail.com, notmuch@notmuchmail.org
Cc:
From: Steven Allen
This appears to have been fixed by commit 89898e43c7ceef28bb3c2116b4d8a3ec96d9c8da in Emacs master.