MANIFEST                  |  1 +
 lib/PublicInbox/Import.pm |  2 ++
 t/nulsubject.t            | 33 +++++++++++++++++++++++++++++++++

diff --git a/MANIFEST b/MANIFEST
index 6d2aecee23c6e6dac765c481c5efff8b24b7aef4..a2fcae9f4a21a646c554e2749cd503952eabc5ce 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -177,6 +177,7 @@ t/msgmap.t
 t/msgtime.t
 t/nntp.t
 t/nntpd.t
+t/nulsubject.t
 t/over.t
 t/perf-nntpd.t
 t/perf-threading.t
diff --git a/lib/PublicInbox/Import.pm b/lib/PublicInbox/Import.pm
index 250a2db31e979054c94df5a0e1dd6ca2d8a5f883..f320c58c6b575023ec94dfcd12e8cbd6910f7af4 100644
--- a/lib/PublicInbox/Import.pm
+++ b/lib/PublicInbox/Import.pm
@@ -405,6 +405,8 @@ 	unless ($parent) {
 		print $w "reset $ref\n" or wfail;
 	}
 
+	# Mime decoding can create nulls replace them with spaces to protect git
+	$subject =~ tr/\0/ /;
 	utf8::encode($subject);
 	print $w "commit $ref\nmark :$commit\n",
 		"author $name <$email> $author_time_raw\n",
diff --git a/t/nulsubject.t b/t/nulsubject.t
new file mode 100644
index 0000000000000000000000000000000000000000..bb05be8589e71ceda4875e7f88cc6cec3bfe36db
--- /dev/null
+++ b/t/nulsubject.t
@@ -0,0 +1,33 @@
+# Copyright (C) 2016-2018 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+use strict;
+use warnings;
+use Test::More;
+use File::Temp qw/tempdir/;
+
+use_ok 'PublicInbox::Import';
+use_ok 'PublicInbox::Git';
+my $tmpdir = tempdir('pi-nulsubject-XXXXXX', TMPDIR => 1, CLEANUP => 1);
+my $git_dir = "$tmpdir/a.git";
+
+{
+	is(system(qw(git init -q --bare), $git_dir), 0, 'git init ok');
+	my $git = PublicInbox::Git->new($git_dir);
+	my $im = PublicInbox::Import->new($git, 'testbox', 'test@example');
+	$im->add(Email::MIME->create(
+		header => [
+			From => 'a@example.com',
+			To => 'b@example.com',
+			'Content-Type' => 'text/plain',
+			Subject => ' A subject line with a null =?iso-8859-1?q?=00?= see!',
+			'Message-ID' => '<null-test.a@example.com>',
+		],
+		body => "hello world\n",
+	));
+	$im->done;
+	is(system(qw(git --git-dir), $git_dir, 'fsck', '--strict'), 0, 'git fsck ok');
+}
+
+done_testing();
+
+1;