diff --git a/plugins/UM3NetworkPrinting/LegacyUM3OutputDevice.py b/plugins/UM3NetworkPrinting/LegacyUM3OutputDevice.py
index e9963c678b..7c76811fd2 100644
--- a/plugins/UM3NetworkPrinting/LegacyUM3OutputDevice.py
+++ b/plugins/UM3NetworkPrinting/LegacyUM3OutputDevice.py
@@ -58,6 +58,7 @@ class LegacyUM3OutputDevice(NetworkedPrinterOutputDevice):
         # This ensures that the messages are only created for devices that actually want to connect.
         self._authentication_requested_message = None
         self._authentication_failed_message = None
+        self._authentication_succeeded_message = None
         self._not_authenticated_message = None
 
         self._sending_gcode = False