diff --git a/src/calibre/devices/mtp/windows/driver.py b/src/calibre/devices/mtp/windows/driver.py
index dbcad94fe0..aaadffbc68 100644
--- a/src/calibre/devices/mtp/windows/driver.py
+++ b/src/calibre/devices/mtp/windows/driver.py
@@ -21,7 +21,7 @@ from calibre.devices.mtp.base import MTPDeviceBase
 class ThreadingViolation(Exception):
 
     def __init__(self):
-        Exception.__init__('You cannot use the MTP driver from a thread other than the '
+        Exception.__init__(self, 'You cannot use the MTP driver from a thread other than the '
                 ' thread in which startup() was called')
 
 def same_thread(func):