error writing from Calibre tot KOBO

Hello,

I have got a problem with Calibre and my KOBO device. Calibre recognises my KOBO but when I want to writ a book from Calibre to my device, I get the following error:

bool' object has no attribute 'startswith'

Traceback (most recent call last):
File "site-packages/calibre/gui2/device.py", line 88, in run
File "site-packages/calibre/gui2/device.py", line 592, in _upload_books
File "calibre_plugins.kobotouch_extended.device.driver" , line 335, in upload_books
File "site-packages/calibre/devices/kobo/driver.py", line 2014, in upload_books
File "calibre_plugins.kobotouch_extended.device.driver" , line 259, in _modify_epub
File "lib/python2.7/posixpath.py", line 254, in expanduser
AttributeError: 'bool' object has no attribute 'startswith'

Is this message familiar to you and do know any solution?

Kind regards,

Theo Jansen