Redmine

Saving a message to a forum or an issue with micro symbol causes an error.

Rendered boards/show.html.erb within layouts/base (15.6ms)
Completed 200 OK in 94ms (Views: 46.8ms | ActiveRecord: 46.8ms)
Started POST "/redmine/boards/3/topics/new" for 127.0.0.1 at 2016-08-10 12:09:12 +0300
Processing by MessagesController#new as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"Sl4Hej3CWWzGsWT4Wr/JZpBXdfGbvYA5vfE+BsGDsqfFgqUOX/FrB2t3gGAmiAlsv4OUViUotQyP8X4mnQwD2Q==", "message"=>{"subject"=>"bug test redmine", "sticky"=>"0", "locked"=>"0", "content"=>"μm is for micrometer\r\n\r\n"}, "commit"=>"Create", "board_id"=>"3"}
  Current user: heikki (id=1)
Completed 500 Internal Server Error in 140ms (ActiveRecord: 140.4ms)

ActiveRecord::StatementInvalid (Mysql2::Error: Incorrect string value: '\xCE\xBCm is...' for column 'content' at row 1: INSERT INTO `messages` (`author_id`, `board_id`, `subject`, `content`, `created_on`, `updated_on`) VALUES (1, 3, 'bug test redmine', 'μm is for micrometer\r\n\r\n', '2016-08-10 12:09:12', '2016-08-10 12:09:12')):
  app/controllers/messages_controller.rb:63:in `new'
  lib/redmine/sudo_mode.rb:63:in `sudo_mode'
 500 Internal Server Error in 47ms (ActiveRecord: 15.6ms)

...

ActiveRecord::StatementInvalid (Mysql2::Error: Incorrect string value: '\xCE\xBCm' for column 'description' at row 1: INSERT INTO `issues` (`project_id`, `author_id`, `tracker_id`, `status_id`, `subject`, `description`, `priority_id`, `updated_on`, `created_on`, `lock_version`) VALUES (84, 1, 15, 1, 'issue microtest', 'μm', 4, '2016-08-10 12:11:59', '2016-08-10 12:11:59', 0)):
  app/models/issue.rb:210:in `create_or_update'
  app/controllers/issues_controller.rb:140:in `create'
  lib/redmine/sudo_mode.rb:63:in `sudo_mode'

Environment:
Redmine version 3.3.0.stable
Ruby version 2.1.8-p440 (2015-12-16) [i386-mingw32]
Rails version 4.2.6
Environment production
Database adapter Mysql2
SCM:
Subversion 1.8.16
Git 2.7.4
Filesystem
Redmine plugins:
no plugin installed