diff --git a/lib/redmine.rb b/lib/redmine.rb
index c15e25891..ce2582024 100644
--- a/lib/redmine.rb
+++ b/lib/redmine.rb
@@ -18,7 +18,6 @@
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 
 require 'redmine/core_ext'
-require 'diff'
 
 begin
   require 'mini_magick' unless Object.const_defined?(:MiniMagick)