lib/PublicInbox/SearchIdx.pm | 2 +-

diff --git a/lib/PublicInbox/SearchIdx.pm b/lib/PublicInbox/SearchIdx.pm
index eb620f44fe990e4c38514d9375fa6328ae30e80d..c36fc6c7dee5307ea803ec17f17ac8af7eb10dc8 100644
--- a/lib/PublicInbox/SearchIdx.pm
+++ b/lib/PublicInbox/SearchIdx.pm
@@ -338,7 +338,7 @@ 	}
 	$doc->add_boolean_term('Q' . $_) for @$mids;
 	for my $l ($hdr->header_raw('List-Id')) {
 		$l =~ /<([^>]+)>/ or next;
-		my $lid = $1;
+		my $lid = lc $1;
 		$doc->add_boolean_term('G' . $lid);
 		index_text($self, $lid, 1, 'XL'); # probabilistic
 	}