doveadm mailbox list permission failure for virtual user

I'm using Dovecot 2.3.21 (47349e2482) on Ubuntu and have convigured virtual mail users. Everything is working finem but a few doevadm commands fail

sudo doveadm mailbox list

returns

doveadm(root): Error: chdir(/root/) failed: Permission denied (euid=1001(vmail) egid=1001(vmail) missing +x perm: /root, dir owned by 0:0 mode=0700)