diff -r 889c43872f4c -r 27e4fd37fea6 Beremiz_service.py
--- a/Beremiz_service.py	Wed Feb 13 13:08:26 2019 +0100
+++ b/Beremiz_service.py	Thu Feb 14 10:06:43 2019 +0100
@@ -435,6 +435,7 @@
         # UI threads can be either the one from WX main loop or
         # worker thread from twisted "threadselect" reactor
         current_id = currentThread().ident
+
         if ui_thread is not None \
             and ui_thread.ident != current_id \
             and (not havetwisted or (
@@ -570,6 +571,7 @@
     # This order ui loop to unblock main thread when ready.
     if havetwisted:
         def signal_uithread_started():
+            global twisted_reactor_thread_id
             twisted_reactor_thread_id = currentThread().ident
             ui_thread_started.release()
         reactor.callLater(0, signal_uithread_started)