DotNetZip trouble with russian encoding

Question

i use DotNetZip in my project.

using (var zip = new ZipFile()) 
{ 
   zip.ProvisionalAlternateEncoding = System.Text.Encoding.GetEncoding(866); 
   zip.AddFile(filename, "directory\\in\\archive"); 
   zip.Save("archive.zip"); 
} 

all ok but when i use method AddDirectoryByName i have a bad directory names.