lib/PublicInbox/Mbox.pm | 3 +++

diff --git a/lib/PublicInbox/Mbox.pm b/lib/PublicInbox/Mbox.pm
index 1e3de5b0d484550b940ce977ff27f8d015ed757e..dc41548b87ce68726dc41aa79bd571589a150641 100644
--- a/lib/PublicInbox/Mbox.pm
+++ b/lib/PublicInbox/Mbox.pm
@@ -138,6 +138,9 @@ 				my $ret = $$bref; # copy :<
 				${$self->{buf}} = '';
 				return $ret;
 			}
+
+			# be fair to other clients on public-inbox-httpd:
+			return '';
 		}
 		$res = $self->{cb}->($self->{opts});
 		$self->{msgs} = $res->{msgs};