diff --git a/GBoxed.xs b/GBoxed.xs
index 5c726aa..1b623df 100644
--- a/GBoxed.xs
+++ b/GBoxed.xs
@@ -287,6 +287,7 @@ gperl_register_boxed_synonym (GType registered_gtype,
 
 	G_LOCK (info_by_gtype);
 
+	warn ("Glib: trying to look up %ld (%s)\n", registered_gtype, g_type_name (registered_gtype));
 	registered_boxed_info = (BoxedInfo *)
 		g_hash_table_lookup (info_by_gtype, (gpointer) registered_gtype);