Mail_Mime: undefined method Mail_mimePart::encodeHeader()

Hello everyone.

I'm developing a mailing list manager, using the package Mail_Mime.

Everything works fine, but when I try sending an e-mail get the following
error:

Fatal error: Call to undefined method Mail_mimePart:: encodeHeader () in /
home / devised / php / Mail / mime.php on line 1316

I don't know if it's a bug or error in my own code, I don't think it's so,
because the error comes from the library mime.php and I dare not to modify
the code.

I hope and give me a quick solution. Thank you.