diff --git a/tests/queue-test.c b/tests/queue-test.c
index 96f21005..6e2e9328 100644
--- a/tests/queue-test.c
+++ b/tests/queue-test.c
@@ -66,7 +66,7 @@ client_test_proxy_destroy(void)
 	assert(registry != NULL);
 	wl_registry_add_listener(registry, &registry_listener,
 				 &counter);
-	wl_display_roundtrip(display);
+	assert(wl_display_roundtrip(display) != -1);
 
 	assert(counter == 1);