lib/PublicInbox/Filter/RubyLang.pm | 29 +++++++++++++++++------------
 t/filter_rubylang.t                | 16 ++++++++++++----

diff --git a/lib/PublicInbox/Filter/RubyLang.pm b/lib/PublicInbox/Filter/RubyLang.pm
index 09aa6aa81d11bd6524e13446cff8dd639f26e49e..57ebbe78f5e173e3a723bb2968da0dac816d7424 100644
--- a/lib/PublicInbox/Filter/RubyLang.pm
+++ b/lib/PublicInbox/Filter/RubyLang.pm
@@ -1,11 +1,10 @@
-# Copyright (C) 2017-2021 all contributors <meta@public-inbox.org>
+# Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 
 # Filter for lists.ruby-lang.org trailers
 package PublicInbox::Filter::RubyLang;
-use base qw(PublicInbox::Filter::Base);
-use strict;
-use warnings;
+use v5.10.1;
+use parent qw(PublicInbox::Filter::Base);
 use PublicInbox::MID qw(mids);
 
 my $l1 = qr/Unsubscribe:\s
@@ -56,16 +55,22 @@ 	if ($altid && !$for_remove) {
 		my $hdr = $mime->header_obj;
 		my $mids = mids($hdr);
 		return $self->REJECT('Message-ID missing') unless (@$mids);
-		my @v = $hdr->header_raw('X-Mail-Count');
 		my $n;
-		foreach (@v) {
-			/\A\s*([0-9]+)\s*\z/ or next;
-			$n = $1;
-			last;
-		}
-		unless (defined $n) {
-			return $self->REJECT('X-Mail-Count not numeric');
+		my @v = $hdr->header_raw('X-Mail-Count'); # old host only
+		if (@v) {
+			for (@v) {
+				/\A\s*([0-9]+)\s*\z/ or next;
+				$n = $1;
+				last;
+			}
+		} else { # new host: nue.mailmanlists.eu
+			for ($hdr->header_str('Subject')) {
+				/\A\[ruby-[^:]+:([0-9]+)\]/ or next;
+				$n = $1;
+				last;
+			}
 		}
+		$n // return $self->REJECT('could not get count not numeric');
 		foreach my $mid (@$mids) {
 			my $r = $altid->mm_alt->mid_set($n, $mid);
 			next if $r == 0;
diff --git a/t/filter_rubylang.t b/t/filter_rubylang.t
index 4e9695e13eb663a361760e43418aa9b5a4c5ff1f..490a215437d7a0495e42ef144035943982f5a4d7 100644
--- a/t/filter_rubylang.t
+++ b/t/filter_rubylang.t
@@ -1,8 +1,7 @@
-# Copyright (C) 2017-2021 all contributors <meta@public-inbox.org>
+#!perl -w
+# Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
-use strict;
-use warnings;
-use Test::More;
+use v5.12;
 use PublicInbox::Eml;
 use PublicInbox::TestCommon;
 use_ok 'PublicInbox::Filter::RubyLang';
@@ -56,6 +55,15 @@
 	$mime = PublicInbox::Eml->new($msg);
 	$ret = $f->delivery($mime);
 	is($ret, 100, "delivery rejected without X-Mail-Count");
+
+	$mime = PublicInbox::Eml->new(<<'EOM');
+Message-ID: <new@host>
+Subject: [ruby-core:13] times
+
+EOM
+	$ret = $f->delivery($mime);
+	is($ret, $mime, "delivery successful");
+	is($mm->num_for('new@host'), 13, 'MM entry created based on Subject');
 }
 
 done_testing();