diff --git a/app/builders/builder.rb b/app/builders/builder.rb
index b43a5cdbe995ab04c9164e525955a90dda0bbe44..8607df0b773842a1ef129d8189748ac155b5a6e6 100644
--- a/app/builders/builder.rb
+++ b/app/builders/builder.rb
@@ -33,7 +33,7 @@ class Builder
   def self.cache_key(rid, last_modified)
     last_modified = Time.at(0).to_s if last_modified.nil?
 
-    rid + '/' + last_modified
+    "#{rid}/#{last_modified}"
   end
 
 end
diff --git a/app/models/learning_object/attachment.rb b/app/models/learning_object/attachment.rb
index 1a4b61ae5209df8ead554e26bac814ad69dd33dc..1aff7410484096c1d5a0551e2b2e897c92bb3ce8 100644
--- a/app/models/learning_object/attachment.rb
+++ b/app/models/learning_object/attachment.rb
@@ -1,8 +1,6 @@
-module LearningObject
-  class Attachment
-    include ActiveModel::Model
+class LearningObject::Attachment
+  include ActiveModel::Model
 
-    #this attributes mirror Dspace bitstream values
-    attr_accessor :id, :name, :link, :retrieve_link, :description, :format, :mime_type, :size
-  end
+  #this attributes mirror Dspace bitstream values
+  attr_accessor :id, :name, :link, :retrieve_link, :description, :format, :mime_type, :size
 end