Type FIle (Rack::Multipart::UploadedFile) replace all non-English letters in file name with underscores ( _ )

Hello, I'm notice, that grape File type validation replace all non-English letters with an underscore symbol
I send:

------WebKitFormBoundarybo7OclPI12IMowot Content-Disposition: form-data; name="file"; filename="привет-hello.png" Content-Type: image/png

and on endpoint I have next validation:

params do
  requires :file, type: File, allow_blank: false, desc: 'Image'
end

but in params I see:

{"file"=> {"filename"=>"\xD0\xBF\xD1\x80\xD0\xB8\xD0\xB2\xD0\xB5\xD1\x82-hello.png", "type"=>"image/png", "name"=>"file", "tempfile"=>#<File:/tmp/RackMultipart20200710-8-11mcjd3.png>, "head"=>"Content-Disposition: form-data; name=\"file\"; filename=\"\xD0\xBF\xD1\x80\xD0\xB8\xD0\xB2\xD0\xB5\xD1\x82-hello.png\"\r\nContent-Type: image/png\r\n"} }

And this "\xD0\xBF\xD1\x80\xD0\xB8\xD0\xB2\xD0\xB5\xD1\x82-hello.png" it same as "____________-hello.png"

Start by reproducing the multipart upload with Rack::Multipart::UploadedFile and the shown params declaration, then trace the File type validation that handles the filename. Confirm whether the filename is being transformed during validation. Done means non-English filename characters are preserved, with coverage for the supplied Cyrillic filename case.