diff --git a/tools/testing/selftests/cgroup/test_kmem.c b/tools/testing/selftests/cgroup/test_kmem.c
index cb47561b4b44..437f2d35f205 100644
--- a/tools/testing/selftests/cgroup/test_kmem.c
+++ b/tools/testing/selftests/cgroup/test_kmem.c
@@ -145,7 +145,7 @@ static int cg_run_in_subcgroups(const char *parent,
 			return -1;
 		}
 
-		if (cg_run(child, fn, NULL)) {
+		if (cg_run(child, fn, arg)) {
 			cg_destroy(child);
 			free(child);
 			return -1;