diff --git a/pack-bitmap.c b/pack-bitmap.c
index e8a82945cc..ee2bfaa4a0 100644
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -1853,8 +1853,8 @@ static void filter_bitmap_blob_none(struct bitmap_index *bitmap_git,
 				   OBJ_BLOB);
 }
 
-static unsigned long get_size_by_pos(struct bitmap_index *bitmap_git,
-				     uint32_t pos)
+static size_t get_size_by_pos(struct bitmap_index *bitmap_git,
+			      uint32_t pos)
 {
 	size_t size;
 	struct object_info oi = OBJECT_INFO_INIT;
@@ -1891,7 +1891,7 @@ static unsigned long get_size_by_pos(struct bitmap_index *bitmap_git,
 			die(_("unable to get size of %s"), oid_to_hex(&obj->oid));
 	}
 
-	return cast_size_t_to_ulong(size);
+	return size;
 }
 
 static void filter_bitmap_blob_limit(struct bitmap_index *bitmap_git,