diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 68f45a96769fe5759f618c4c6ee430f3b9530572..5186b7710430bacfdbd261e86a7352a7cf75f18f 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -778,7 +778,7 @@ static struct bpf_map *bpf_object__add_map(struct bpf_object *obj)
 	if (obj->nr_maps < obj->maps_cap)
 		return &obj->maps[obj->nr_maps++];
 
-	new_cap = max(4ul, obj->maps_cap * 3 / 2);
+	new_cap = max((size_t)4, obj->maps_cap * 3 / 2);
 	new_maps = realloc(obj->maps, new_cap * sizeof(*obj->maps));
 	if (!new_maps) {
 		pr_warning("alloc maps for object failed\n");