diff --git a/sha1_file.c b/sha1_file.c
index b44f524..3da70ac 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -1964,7 +1964,6 @@
 	origlen = path->len;
 	strbuf_complete(path, '/');
 	strbuf_addf(path, "%02x", subdir_nr);
-	baselen = path->len;
 
 	dir = opendir(path->buf);
 	if (!dir) {
@@ -1975,15 +1974,18 @@
 	}
 
 	oid.hash[0] = subdir_nr;
+	strbuf_addch(path, '/');
+	baselen = path->len;
 
 	while ((de = readdir(dir))) {
+		size_t namelen;
 		if (is_dot_or_dotdot(de->d_name))
 			continue;
 
+		namelen = strlen(de->d_name);
 		strbuf_setlen(path, baselen);
-		strbuf_addf(path, "/%s", de->d_name);
-
-		if (strlen(de->d_name) == GIT_SHA1_HEXSZ - 2 &&
+		strbuf_add(path, de->d_name, namelen);
+		if (namelen == GIT_SHA1_HEXSZ - 2 &&
 		    !hex_to_bytes(oid.hash + 1, de->d_name,
 				  GIT_SHA1_RAWSZ - 1)) {
 			if (obj_cb) {
@@ -2002,7 +2004,7 @@
 	}
 	closedir(dir);
 
-	strbuf_setlen(path, baselen);
+	strbuf_setlen(path, baselen - 1);
 	if (!r && subdir_cb)
 		r = subdir_cb(subdir_nr, path->buf, data);
 
diff --git a/t/perf/p4211-line-log.sh b/t/perf/p4211-line-log.sh
index e0ed059..392bcc0 100755
--- a/t/perf/p4211-line-log.sh
+++ b/t/perf/p4211-line-log.sh
@@ -35,4 +35,8 @@
 	git log --oneline --raw --parents >/dev/null
 '
 
+test_perf 'git log --oneline --raw --parents -1000' '
+	git log --oneline --raw --parents -1000 >/dev/null
+'
+
 test_done