acts-as-taggable-on version problem

[ghost]

Redmine version 2.6.9.stable
Ruby version 2.0.0-p598 (2014-11-13) [i686-linux]
Rails version 3.2.22

I'm using redmine_knowledgebase pluging. This plugin use redmine_acts_as_taggable_on.
It require the version of acts-as-taggable-on is <2.5 and >= 2.3
But this plugin is require higher version. So I can't install this plugin.

Do you have the solution for this problem?
Thanks