diff --git a/install/debian/9/dovecot/conf.d/15-mailboxes.conf b/install/debian/9/dovecot/conf.d/15-mailboxes.conf
index 7b2bab97..9014bdab 100644
--- a/install/debian/9/dovecot/conf.d/15-mailboxes.conf
+++ b/install/debian/9/dovecot/conf.d/15-mailboxes.conf
@@ -4,6 +4,7 @@
 
 # NOTE: Assumes "namespace inbox" has been defined in 10-mail.conf.
 namespace inbox {
+  inbox = yes
   mailbox Drafts {
     special_use = \Drafts
     auto = subscribe