diff --git a/midx.c b/midx.c
index 64a051cca1..25350152f1 100644
--- a/midx.c
+++ b/midx.c
@@ -311,17 +311,19 @@ int prepare_midx_pack(struct repository *r, struct multi_pack_index *m,
 int nth_bitmapped_pack(struct repository *r, struct multi_pack_index *m,
 		       struct bitmapped_pack *bp, uint32_t pack_int_id)
 {
+	uint32_t local_pack_int_id = midx_for_pack(&m, pack_int_id);
+
 	if (!m->chunk_bitmapped_packs)
 		return error(_("MIDX does not contain the BTMP chunk"));
 
 	if (prepare_midx_pack(r, m, pack_int_id))
 		return error(_("could not load bitmapped pack %"PRIu32), pack_int_id);
 
-	bp->p = m->packs[pack_int_id];
+	bp->p = m->packs[local_pack_int_id];
 	bp->bitmap_pos = get_be32((char *)m->chunk_bitmapped_packs +
-				  MIDX_CHUNK_BITMAPPED_PACKS_WIDTH * pack_int_id);
+				  MIDX_CHUNK_BITMAPPED_PACKS_WIDTH * local_pack_int_id);
 	bp->bitmap_nr = get_be32((char *)m->chunk_bitmapped_packs +
-				 MIDX_CHUNK_BITMAPPED_PACKS_WIDTH * pack_int_id +
+				 MIDX_CHUNK_BITMAPPED_PACKS_WIDTH * local_pack_int_id +
 				 sizeof(uint32_t));
 	bp->pack_int_id = pack_int_id;