Hiki Error

invalid multibyte character (ArgumentError)
/projects/www/dbreading/hiki/filter/bayes_filter/bayes.rb:20:in `block in <module:EUC>'
/projects/www/dbreading/hiki/filter/bayes_filter/bayes.rb:20:in `<module:EUC>'
/projects/www/dbreading/hiki/filter/bayes_filter/bayes.rb:15:in `<module:CHARSET>'
/projects/www/dbreading/hiki/filter/bayes_filter/bayes.rb:7:in `<module:Bayes>'
/projects/www/dbreading/hiki/filter/bayes_filter/bayes.rb:6:in `<top (required)>'
/usr/local/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
/usr/local/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
/projects/www/dbreading/hiki/filter/bayes_filter.rb:5:in `<top (required)>'
/usr/local/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
/usr/local/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
/projects/www/dbreading/hiki/filter.rb:26:in `block in require_filters'
/projects/www/dbreading/hiki/filter.rb:24:in `each'
/projects/www/dbreading/hiki/filter.rb:24:in `require_filters'
/projects/www/dbreading/hiki/filter.rb:67:in `<top (required)>'
/usr/local/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
/usr/local/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
/projects/www/dbreading/hiki/command.rb:10:in `<top (required)>'
/usr/local/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
/usr/local/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
/projects/www/dbreading/hiki/config.rb:16:in `<top (required)>'
/usr/local/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
/usr/local/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
/projects/www/dbreading/hiki.cgi:18:in `<main>'