GLib-GObject-CRITICAL **: g_object_unref: assertion 'G_IS_OBJECT (object)' failed

When running cross language tests with a c_glib server, I see g_object_unref assertion errors like these in the output logs:

(lt-test_server:54378): GLib-GObject-CRITICAL **: g_object_unref: assertion 'G_IS_OBJECT (object)' failed