1 files changed, 5 insertions, 4 deletions
diff --git a/lib/gitlab/diff/highlight.rb b/lib/gitlab/diff/highlight.rb
index 9283b5e185d..a7f925ce134 100644
--- a/lib/gitlab/diff/highlight.rb
+++ b/lib/gitlab/diff/highlight.rb
@@ -16,9 +16,10 @@ module Gitlab
       end
 
       def highlight
-        @diff_lines.each_with_index do |diff_line, i|
+        @diff_lines.map.with_index do |diff_line, i|
+          diff_line = diff_line.dup
           # ignore highlighting for "match" lines
-          next if diff_line.type == 'match' || diff_line.type == 'nonewline'
+          next diff_line if diff_line.type == 'match' || diff_line.type == 'nonewline'
 
           rich_line = highlight_line(diff_line, i)
 
@@ -27,9 +28,9 @@ module Gitlab
           end
 
           diff_line.text = rich_line.html_safe
-        end
 
-        @diff_lines
+          diff_line
+        end
       end
 
       private