diff --git a/archive-tar.c b/archive-tar.c
index 181da4e843..3d76977c3f 100644
--- a/archive-tar.c
+++ b/archive-tar.c
@@ -149,7 +149,7 @@ static void strbuf_append_ext_header(struct strbuf *sb, const char *keyword,
 
 	/* "%u %s=%s\n" */
 	len = 1 + 1 + strlen(keyword) + 1 + valuelen + 1;
-	for (tmp = len; tmp > 9; tmp /= 10)
+	for (tmp = 1; len / 10 >= tmp; tmp *= 10)
 		len++;
 
 	strbuf_grow(sb, len);
diff --git a/t/t5004-archive-corner-cases.sh b/t/t5004-archive-corner-cases.sh
index 2f15d1899d..4966a74b4d 100755
--- a/t/t5004-archive-corner-cases.sh
+++ b/t/t5004-archive-corner-cases.sh
@@ -217,7 +217,7 @@ build_tree() {
 	' "$1"
 }
 
-test_expect_failure 'tar archive with long paths' '
+test_expect_success 'tar archive with long paths' '
 	blob=$(echo foo | git hash-object -w --stdin) &&
 	tree=$(build_tree $blob | git mktree) &&
 	git archive -o long_paths.tar $tree 2>stderr &&