lib/PublicInbox/GzipFilter.pm | 3 ++-

diff --git a/lib/PublicInbox/GzipFilter.pm b/lib/PublicInbox/GzipFilter.pm
index e37f1f76bd4a886431224ed38aa8a3f838cc50b1..c586d2f885dfe3bcdf3aff08f4ab87f7ac5275b7 100644
--- a/lib/PublicInbox/GzipFilter.pm
+++ b/lib/PublicInbox/GzipFilter.pm
@@ -149,10 +149,11 @@ 	my $self = $_[0]; # $_[1] => final input (optional)
 	my $zbuf = delete $self->{zbuf};
 	my $gz = delete $self->{gz};
 	my $err;
-	if (defined $_[1]) {
+	if (defined $_[1]) { # it's a bug iff $gz is undef w/ $_[1]
 		$err = $gz->deflate($_[1], $zbuf);
 		die "gzip->deflate: $err" if $err != Z_OK;
 	}
+	$gz // return; # not a bug, recursing on DS->write failure
 	$err = $gz->flush($zbuf);
 	die "gzip->flush: $err" if $err != Z_OK;
 	$zbuf;