lib/PublicInbox/V2Writable.pm | 1 +

diff --git a/lib/PublicInbox/V2Writable.pm b/lib/PublicInbox/V2Writable.pm
index 92d2672c78c478f886a3bd7d5f9cb8c238f3456b..4dd14331a78f0b46eeadce951e388e47794be3b9 100644
--- a/lib/PublicInbox/V2Writable.pm
+++ b/lib/PublicInbox/V2Writable.pm
@@ -676,6 +676,7 @@ 		my $n = $mm_tmp->num_for($mid);
 		if (defined $n && $n > $num) {
 			$mid0 = $mid;
 			$num = $n;
+			$self->{mm}->mid_set($num, $mid0);
 		}
 	}
 	if (!defined($mid0) && $regen && !$del) {