Fails to clean password-protected PDF file

When cleaning a pdf file which is "protected" by a password, the following traceback is issued :

Command Line Error: Incorrect password
 Traceback (most recent call last):
  File "./mat", line 150, in 
    main()
  File "./mat", line 143, in main
    add2archive=args.add2archive, low_pdf_quality=args.low_pdf_quality)
  File "/home/fr33tux/mat/MAT/mat.py", line 186, in create_class_file
    return stripper_class(filename, parser, mime, backup, is_writable, **kwargs)
  File "/home/fr33tux/mat/MAT/office.py", line 122, in __init__
    self.document = Poppler.Document.new_from_file(uri, self.password)
  File "/usr/lib/python2.7/dist-packages/gi/types.py", line 76, in constructor
    return info.invoke(cls, *args, **kwargs)

(from redmine: created on 2014-01-28)