+test_expect_failure 'tag with NUL in header' '
+ sha=$(git rev-parse HEAD) &&
+ q_to_nul >tag-NUL-header <<-EOF &&
+ object $sha
+ type commit
+ tag contains-Q-in-header
+ tagger T A Gger <tagger@example.com> 1234567890 -0000
+
+ This is an invalid tag.
+ EOF
+
+ tag=$(git hash-object --literally -t tag -w --stdin <tag-NUL-header) &&
+ test_when_finished "remove_object $tag" &&
+ echo $tag >.git/refs/tags/wrong &&
+ test_when_finished "git update-ref -d refs/tags/wrong" &&
+ test_must_fail git fsck --tags 2>out &&
+ cat out &&
+ grep "error in tag $tag.*unterminated header: NUL at offset" out
+'
+