diff --git a/plugins/USBPrinting/USBPrinterOutputDevice.py b/plugins/USBPrinting/USBPrinterOutputDevice.py
index a28bf06b77..580bbf06df 100644
--- a/plugins/USBPrinting/USBPrinterOutputDevice.py
+++ b/plugins/USBPrinting/USBPrinterOutputDevice.py
@@ -19,8 +19,8 @@ from PyQt5.QtCore import QUrl, pyqtSlot, pyqtSignal, pyqtProperty
 from UM.i18n import i18nCatalog
 catalog = i18nCatalog("cura")
 
-class USBPrinterOutputDevice(PrinterOutputDevice):
 
+class USBPrinterOutputDevice(PrinterOutputDevice):
     def __init__(self, serial_port):
         super().__init__(serial_port)
         self.setName(catalog.i18nc("@item:inmenu", "USB printing"))
@@ -562,6 +562,11 @@ class USBPrinterOutputDevice(PrinterOutputDevice):
         if ";" in line:
             line = line[:line.find(";")]
         line = line.strip()
+
+        # Don't send empty lines. But we do have to send something, so send m105 instead.
+        if line == "":
+            line = "M105"
+
         try:
             if line == "M0" or line == "M1":
                 line = "M105"  # Don't send the M0 or M1 to the machine, as M0 and M1 are handled as an LCD menu pause.
diff --git a/plugins/USBPrinting/USBPrinterOutputDeviceManager.py b/plugins/USBPrinting/USBPrinterOutputDeviceManager.py
index eb0193c0c0..5b1d0b8dac 100644
--- a/plugins/USBPrinting/USBPrinterOutputDeviceManager.py
+++ b/plugins/USBPrinting/USBPrinterOutputDeviceManager.py
@@ -236,8 +236,7 @@ class USBPrinterOutputDeviceManager(QObject, OutputDevicePlugin, Extension):
                 self.getOutputDeviceManager().removeOutputDevice(serial_port)
             self.connectionStateChanged.emit()
         except KeyError:
-            pass  # no output device by this device_id found in connection list.
-
+            Logger.log("w", "Connection state of %s changed, but it was not found in the list")
 
     @pyqtProperty(QObject , notify = connectionStateChanged)
     def connectedPrinterList(self):