lib/PublicInbox/Mbox.pm   | 2 +-
 lib/PublicInbox/MboxGz.pm | 2 +-

diff --git a/lib/PublicInbox/Mbox.pm b/lib/PublicInbox/Mbox.pm
index 42cedd15f5dead4a73170094327501f12111d983..c50a118b2b6367200767ea929ba97596bd1713c5 100644
--- a/lib/PublicInbox/Mbox.pm
+++ b/lib/PublicInbox/Mbox.pm
@@ -18,7 +18,7 @@
 sub subject_fn ($) {
 	my ($hdr) = @_;
 	my $fn = $hdr->header('Subject');
-	return 'no-subject' unless defined($fn);
+	return 'no-subject' if (!defined($fn) || $fn eq '');
 
 	# no need for full Email::MIME, here
 	if ($fn =~ /=\?/) {
diff --git a/lib/PublicInbox/MboxGz.pm b/lib/PublicInbox/MboxGz.pm
index 1621cff8f3f99511fa20ff91469fdc14e32126d6..ef560426a5c7e1af697c2c5eb242ea2964beac63 100644
--- a/lib/PublicInbox/MboxGz.pm
+++ b/lib/PublicInbox/MboxGz.pm
@@ -23,7 +23,7 @@ 	my ($class, $ctx, $cb, $fn) = @_;
 	my $body = $class->new($ctx, $cb);
 	# http://www.iana.org/assignments/media-types/application/gzip
 	my @h = qw(Content-Type application/gzip);
-	if ($fn) {
+	if (defined $fn && $fn ne '') {
 		$fn = to_filename($fn);
 		push @h, 'Content-Disposition', "inline; filename=$fn.mbox.gz";
 	}