diff -r aba122ac2d40 -r fa3d9c22497c plugins/redmine_bibliography/init.rb
--- a/plugins/redmine_bibliography/init.rb
+++ b/plugins/redmine_bibliography/init.rb
@@ -2,6 +2,8 @@
 
 require 'bibtex'
 require 'citeproc'
+require 'citeproc/ruby'
+require 'csl/styles'
 
 # Patches to the Redmine core.
 ActionDispatch::Callbacks.to_prepare do