diff --git a/plugins/USBPrinting/PrinterConnection.py b/plugins/USBPrinting/PrinterConnection.py
index 19c5b5c07a..1d651516c5 100644
--- a/plugins/USBPrinting/PrinterConnection.py
+++ b/plugins/USBPrinting/PrinterConnection.py
@@ -173,6 +173,10 @@ class PrinterConnection(SignalEmitter):
             Logger.log("i", "Could not establish connection on %s: %s. Device is not arduino based." %(self._serial_port,str(e)))
         except Exception as e:
             Logger.log("i", "Could not establish connection on %s, unknown reasons.  Device is not arduino based." % self._serial_port)
+
+        if not self._serial or not programmer.serial:
+            self._is_connecting = False
+            return
         
         # If the programmer connected, we know its an atmega based version. Not all that usefull, but it does give some debugging information.
         for baud_rate in self._getBaudrateList(): # Cycle all baud rates (auto detect)