Redmine

I have upgraded from Redmine 2.5.2 to 3.1.0 and I'm currently running into an Internal Server Error when creating/copying issues. The log/production.log shows:

NameError (undefined method `_run_save_callbacks' for class `Issue'):
  app/models/issue.rb:175:in `create_or_update'
  app/controllers/issues_controller.rb:141:in `create'
  lib/redmine/sudo_mode.rb:63:in `sudo_mode'

Configuration Info

Environment:
  Redmine version                3.1.0.stable
  Ruby version                   1.9.3-p392 (2013-02-22) [i686-linux]
  Rails version                  4.2.3
  Environment                    production
  Database adapter               PostgreSQL
SCM:
  Subversion                     1.6.17
  Cvs                            1.12.13
  Git                            1.7.10.4
  Filesystem                     
Redmine plugins:
  redmine_agile                  1.3.10
  redmine_better_gantt_chart     0.9.0
  redmine_checklists             3.1.1
  redmine_github_hook            2.2.0
  redmine_gitlab_hook            0.1.3
  redmine_issue_templates        0.1.0
  redmine_mylyn_connector        2.8.2.stable
  redmine_spent_time             3.0.2
  redmine_stealth                0.6.0
  redmine_testlinklink           1.0.0
  redmine_wiki_extensions        0.7.0
  redmine_wiki_lists             0.0.6