ajax breaking multiline select habtm parameters

I have a journalist and publication model related with a habtm. In the edit journalist form there is a multiline select for publications.

When :remote => false this works well, the parameter for the publications looks like:

publication_ids"=>["", “4256”,“4271”]

BUT if I use :remote => true the parameter array allways has size = 2:

publication_ids"=>["", “4256,4271”]

The quotes are missing and only the first relation gets saved.

Since the problem is only in the ajax call I don’t think I have done anything wrong.

Rails 3.2.12, Ruby 1.9.3-p374. This is quite an old application so I use prototype.

Hs anyone experienced this, what can be the cause?