lib/PublicInbox/IMAP.pm | 6 ++++++
 t/imapd.t               | 3 ++-

diff --git a/lib/PublicInbox/IMAP.pm b/lib/PublicInbox/IMAP.pm
index 54c616eee2fd307f39a102384be59dcd9416f99e..0852ffab868dc61bfba42d9ca8f1858911ddcfd0 100644
--- a/lib/PublicInbox/IMAP.pm
+++ b/lib/PublicInbox/IMAP.pm
@@ -121,6 +121,12 @@ 	my ($self, $tag) = @_; # ignore ($user, $password) = ($_[2], $_[3])
 	login_success($self, $tag);
 }
 
+sub cmd_close ($$) {
+	my ($self, $tag) = @_;
+	delete $self->{ibx} ? "$tag OK Close done\r\n"
+				: "$tag BAD No mailbox\r\n";
+}
+
 sub cmd_logout ($$) {
 	my ($self, $tag) = @_;
 	delete $self->{logged_in};
diff --git a/t/imapd.t b/t/imapd.t
index 1ec0d5c370fcd6220e2c95d5f527f605bf598d19..8172a91923d3777de714a989ed03d5716942f75d 100644
--- a/t/imapd.t
+++ b/t/imapd.t
@@ -327,7 +327,8 @@ 			or BAIL_OUT "FETCH $@";
 is($r2->{2}->{'BODY[HEADER.FIELDS (MESSAGE-ID)]'},
 	'Message-ID: <20200418222508.GA13918@dcvr>'."\r\n\r\n",
 	'BODY.PEEK[HEADER.FIELDS ...] drops .PEEK');
-
+ok($mic->close, 'CLOSE works');
+ok(!$mic->close, 'CLOSE not idempotent');
 ok($mic->logout, 'logged out');
 
 $td->kill;