diff --git a/core/config/initializers/user_class_extensions.rb b/core/config/initializers/user_class_extensions.rb
index 7bed68c4181..3481abf898f 100644
--- a/core/config/initializers/user_class_extensions.rb
+++ b/core/config/initializers/user_class_extensions.rb
@@ -1,11 +1,12 @@
-if Spree.user_class
-  Spree.user_class.class_eval do
-    has_and_belongs_to_many :roles, :join_table => 'spree_roles_users'
+Spree::Core::Engine.to_prepare do
+  if Spree.user_class
+    Spree.user_class.class_eval do
+      has_and_belongs_to_many :roles, :join_table => 'spree_roles_users'
 
-    # has_spree_role? simply needs to return true or false whether a user has a role or not.
-    def has_spree_role?(role_in_question)
-      roles.any? { |role| role.name == role_in_question.to_s }
+      # has_spree_role? simply needs to return true or false whether a user has a role or not.
+      def has_spree_role?(role_in_question)
+        roles.any? { |role| role.name == role_in_question.to_s }
+      end
     end
   end
 end
-