diff --git a/openbsc/tests/gbproxy/gbproxy_test.c b/openbsc/tests/gbproxy/gbproxy_test.c
index 964c6da..5363749 100644
--- a/openbsc/tests/gbproxy/gbproxy_test.c
+++ b/openbsc/tests/gbproxy/gbproxy_test.c
@@ -1571,6 +1571,12 @@
 	OSMO_ASSERT(gbprox_set_patch_filter(&cfg, NULL, &err_msg) == 0);
 	OSMO_ASSERT(cfg.check_imsi == 0);
 
+	OSMO_ASSERT(gbprox_set_patch_filter(&cfg, filter_re2, &err_msg) == 0);
+	OSMO_ASSERT(cfg.check_imsi == 1);
+
+	gbprox_clear_patch_filter(&cfg);
+	OSMO_ASSERT(cfg.check_imsi == 0);
+
 	peer = gbproxy_peer_alloc(&cfg, 20);
 
 	OSMO_ASSERT(gbprox_set_patch_filter(&cfg, filter_re2, &err_msg) == 0);