Rails truncate strings in an array

In my app I'm trying to truncate a string of tags that get displayed. I've tried doing it this way:

<%= @medium.marker_list.map { |m| 
      link_to truncate('+ ' + m.titleize, length: 5), 
              :controller => "media", :action => "index", :media => m 
    }.join(' ').html_safe %>

The problem is that if any string is greater than 5 it replaces the whole string with ellipsis instead of replacing just the characters that are longer than the set length.

How do I get this to output correctly?

I'm creating the tags through the acts-as-taggable gem.

** EDIT **

So if I have list of tags like this: example, test, product, listing

it returns this: ..., test, ..., ...

when it should be returning this: examp...,test,produ..., listi...