lib/PublicInbox/InboxIdle.pm | 5 +++++

diff --git a/lib/PublicInbox/InboxIdle.pm b/lib/PublicInbox/InboxIdle.pm
index f1cbc012f2bc6bb3bfb6420082282e2ea919d97f..84b6d26f98dfb28fd80dd2bfbca8a70d07e873d5 100644
--- a/lib/PublicInbox/InboxIdle.pm
+++ b/lib/PublicInbox/InboxIdle.pm
@@ -39,6 +39,11 @@ 	if (my $w = $cur->[1] = $inot->watch($lock, $IN_MODIFY)) {
 		$self->{on_unlock}->{$w->name} = $ibx;
 	} else {
 		warn "E: ".ref($inot)."->watch($lock, IN_MODIFY) failed: $!\n";
+		if ($!{ENOSPC} && $^O eq 'linux') {
+			warn <<"";
+I: consider increasing /proc/sys/fs/inotify/max_user_watches
+
+		}
 	}
 
 	# TODO: detect deleted packs (and possibly other files)