diff --git a/lib/gitlab/diff/highlight.rb b/lib/gitlab/diff/highlight.rb
index 964c89de6c6..9283b5e185d 100644
--- a/lib/gitlab/diff/highlight.rb
+++ b/lib/gitlab/diff/highlight.rb
@@ -7,8 +7,8 @@ module Gitlab
 
       def initialize(diff_lines)
         if diff_lines.is_a?(Gitlab::Diff::File)
-          @diff_file = diff_file
-          @diff_lines = diff_file.diff_lines
+          @diff_file = diff_lines
+          @diff_lines = @diff_file.diff_lines
         else
           @diff_lines = diff_lines
         end