lib/PublicInbox/WatchMaildir.pm | 2 +-

diff --git a/lib/PublicInbox/WatchMaildir.pm b/lib/PublicInbox/WatchMaildir.pm
index 5176ef69db9e9d698ceb4a33efadc019739b80f9..1c7ac6c0df67baf83a604a7cc443d62ce858a0d6 100644
--- a/lib/PublicInbox/WatchMaildir.pm
+++ b/lib/PublicInbox/WatchMaildir.pm
@@ -5,7 +5,7 @@ # ref: https://cr.yp.to/proto/maildir.html
 #	http://wiki2.dovecot.org/MailboxFormat/Maildir
 package PublicInbox::WatchMaildir;
 use strict;
-use warnings;
+use v5.10.1;
 use PublicInbox::Eml;
 use PublicInbox::InboxWritable qw(eml_from_path warn_ignore_cb);
 use PublicInbox::Filter::Base qw(REJECT);