Redmine

I'm not sure if this is by design or if it is a problem. When grouping issues on Target Version, Redmine puts the issues with no Target Version first ("blank").

E.g.

• (blank)
• Version 1
• Version 2
• ...

On one of our projects, however, the "blank" group is placed inbetween versions:

I've looked at the sorting/grouping settings but everything seems OK.

Is there an explanation for this behaviour?

Our Redmine:

Environment:
  Redmine version                3.0.3.stable
  Ruby version                   1.9.3-p484 (2013-11-22) [x86_64-linux]
  Rails version                  4.2.1
  Environment                    production
  Database adapter               Mysql2
SCM:
  Filesystem                     
Redmine plugins:
  redmine_agile                  1.3.9

Thanks in advance!