diff --git a/pack-bitmap.c b/pack-bitmap.c
index c81d323329..1a067885a1 100644
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -169,7 +169,7 @@ static int load_bitmap_header(struct bitmap_index *index)
 
 static struct stored_bitmap *store_bitmap(struct bitmap_index *index,
 					  struct ewah_bitmap *root,
-					  const unsigned char *hash,
+					  const struct object_id *oid,
 					  struct stored_bitmap *xor_with,
 					  int flags)
 {
@@ -181,7 +181,7 @@ static struct stored_bitmap *store_bitmap(struct bitmap_index *index,
 	stored->root = root;
 	stored->xor = xor_with;
 	stored->flags = flags;
-	oidread(&stored->oid, hash);
+	oidcpy(&stored->oid, oid);
 
 	hash_pos = kh_put_oid_map(index->bitmaps, stored->oid, &ret);
 
@@ -189,7 +189,7 @@ static struct stored_bitmap *store_bitmap(struct bitmap_index *index,
 	 * because the SHA1 already existed on the map. this is bad, there
 	 * shouldn't be duplicated commits in the index */
 	if (ret == 0) {
-		error("Duplicate entry in bitmap index: %s", hash_to_hex(hash));
+		error("Duplicate entry in bitmap index: %s", oid_to_hex(oid));
 		return NULL;
 	}
 
@@ -221,13 +221,13 @@ static int load_bitmap_entries_v1(struct bitmap_index *index)
 		struct ewah_bitmap *bitmap = NULL;
 		struct stored_bitmap *xor_bitmap = NULL;
 		uint32_t commit_idx_pos;
-		const unsigned char *sha1;
+		struct object_id oid;
 
 		commit_idx_pos = read_be32(index->map, &index->map_pos);
 		xor_offset = read_u8(index->map, &index->map_pos);
 		flags = read_u8(index->map, &index->map_pos);
 
-		sha1 = nth_packed_object_sha1(index->pack, commit_idx_pos);
+		nth_packed_object_id(&oid, index->pack, commit_idx_pos);
 
 		bitmap = read_bitmap_1(index);
 		if (!bitmap)
@@ -244,7 +244,7 @@ static int load_bitmap_entries_v1(struct bitmap_index *index)
 		}
 
 		recent_bitmaps[i % MAX_XOR_OFFSET] = store_bitmap(
-			index, bitmap, sha1, xor_bitmap, flags);
+			index, bitmap, &oid, xor_bitmap, flags);
 	}
 
 	return 0;