diff --git a/tests/tdef/tdef_test.c b/tests/tdef/tdef_test.c
index 276330a..9c0808e 100644
--- a/tests/tdef/tdef_test.c
+++ b/tests/tdef/tdef_test.c
@@ -475,7 +475,7 @@
 	log_set_print_category(osmo_stderr_target, 1);
 	log_set_use_color(osmo_stderr_target, 0);
 
-	osmo_fsm_register(&test_tdef_fsm);
+	OSMO_ASSERT(osmo_fsm_register(&test_tdef_fsm) == 0);
 
 	test_tdef_get(argc > 1);
 	test_tdef_get_nonexisting();