lib/PublicInbox/WWW.pm | 2 +-

diff --git a/lib/PublicInbox/WWW.pm b/lib/PublicInbox/WWW.pm
index c99c25f827cc79db447044c6a5ca639e29add4d9..278d786d13755242b0edc72b1e0591b3040cc047 100644
--- a/lib/PublicInbox/WWW.pm
+++ b/lib/PublicInbox/WWW.pm
@@ -51,7 +51,7 @@ 	# thread display
 	} elsif ($path_info =~ m!$LISTNAME_RE/t/(\S+)/\z!o) {
 		invalid_list_mid(\%ctx, $1, $2) || get_thread(\%ctx);
 
-	} elsif ($path_info =~ m!$LISTNAME_RE/t/(\S+)/mbox(\.gz)?\z!x) {
+	} elsif ($path_info =~ m!$LISTNAME_RE/t/(\S+)/mbox(\.gz)?\z!o) {
 		my $sfx = $3;
 		invalid_list_mid(\%ctx, $1, $2) ||
 			get_thread_mbox(\%ctx, $sfx);