diff --git a/src/escpos/printer.py b/src/escpos/printer.py
index ed38d4f..b20876b 100644
--- a/src/escpos/printer.py
+++ b/src/escpos/printer.py
@@ -72,7 +72,7 @@ class Usb(Escpos):
         # only libusb1 backend implements the methods is_kernel_driver_active()
         # and detach_kernel_driver(). This change helps enable this
         # library to work on Windows.
-        if sef.device.backend.__module__.endswith("libusb1"):
+        if self.device.backend.__module__.endswith("libusb1"):
             check_driver = None
 
             try: