diff --git a/lib/gitlab/incoming_email.rb b/lib/gitlab/incoming_email.rb
index 0ea42148c5844368624326591194db45ca2f9f69..a492f90430394cc4a6f0cb3a9fedbb96b7f871c1 100644
--- a/lib/gitlab/incoming_email.rb
+++ b/lib/gitlab/incoming_email.rb
@@ -35,12 +35,14 @@ module Gitlab
       end
 
       def key_from_fallback_message_id(mail_id)
-        message_id_regexp = /\Areply\-(.+)@#{Gitlab.config.gitlab.host}\z/
+        message_id_regexp =
+          /\Areply\-(.+)@#{Gitlab.config.gitlab.host}\z/.freeze
 
         mail_id[message_id_regexp, 1]
       end
 
       def scan_fallback_references(references)
+        # It's looking for each <...>
         references.scan(/(?!<)[^<>]+(?=>)/.freeze)
       end