diff --git a/sha1_name.c b/sha1_name.c
index 24894b3dbe..0185c6081a 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -150,31 +150,14 @@ static int match_sha(unsigned len, const unsigned char *a, const unsigned char *
 static void unique_in_pack(struct packed_git *p,
 			   struct disambiguate_state *ds)
 {
-	uint32_t num, last, i, first = 0;
+	uint32_t num, i, first = 0;
 	const struct object_id *current = NULL;
 
 	if (open_pack_index(p) || !p->num_objects)
 		return;
 
 	num = p->num_objects;
-	last = num;
-	while (first < last) {
-		uint32_t mid = first + (last - first) / 2;
-		const unsigned char *current;
-		int cmp;
-
-		current = nth_packed_object_sha1(p, mid);
-		cmp = hashcmp(ds->bin_pfx.hash, current);
-		if (!cmp) {
-			first = mid;
-			break;
-		}
-		if (cmp > 0) {
-			first = mid+1;
-			continue;
-		}
-		last = mid;
-	}
+	bsearch_pack(&ds->bin_pfx, p, &first);
 
 	/*
 	 * At this point, "first" is the location of the lowest object