diff --git a/scripts/tcp5p28.gd b/scripts/tcp5p28.gd
index dabf436f..b8a4d510 100644
--- a/scripts/tcp5p28.gd
+++ b/scripts/tcp5p28.gd
@@ -212,3 +212,6 @@ class TCP5P28 extends unit.Unit:
         var data_to_send: PackedByteArray = create_header(data_len)
         data_to_send.append_array(data_tx)
         tx_stack.append(data_to_send)
+
+    func on_setting_changed():
+        ext_cu = ProjectSettings.get_setting('application/config/external_cu', false)