diff --git a/plugins/UM3NetworkPrinting/NetworkPrinterOutputDevice.py b/plugins/UM3NetworkPrinting/NetworkPrinterOutputDevice.py
index 21e23ead93..0dd31652ce 100755
--- a/plugins/UM3NetworkPrinting/NetworkPrinterOutputDevice.py
+++ b/plugins/UM3NetworkPrinting/NetworkPrinterOutputDevice.py
@@ -200,7 +200,7 @@ class NetworkPrinterOutputDevice(PrinterOutputDevice):
 
     def _onAuthenticationRequired(self, reply, authenticator):
         if self._authentication_id is not None and self._authentication_key is not None:
-            Logger.log("d", "Authentication was required. Setting up authenticator with ID %s and key", self._authentication_id, self._getSafeAuthKey())
+            Logger.log("d", "Authentication was required. Setting up authenticator with ID %s and key %s", self._authentication_id, self._getSafeAuthKey())
             authenticator.setUser(self._authentication_id)
             authenticator.setPassword(self._authentication_key)
         else: