mechanize test failure: undefined method last

[gogainda]

TestMechanizeParser#test_extract_filename_content_disposition:
NoMethodError: undefined method `last' for nil:NilClass
    /Users/novoi/tmp/mechanize/lib/mechanize/parser.rb:129:in `extract_filename'
    /Users/novoi/tmp/mechanize/test/test_mechanize_parser.rb:37:in `test_extract_filename_content_disposition'

it happens here:

filename = content_disposition.filename
        filename = filename.rpartition(/[\\\/]/).last
        handled = true

If filename doesn't match the rpatition regexptit returns nil instead of ["", "", original_str]