1 files changed, 6 insertions, 16 deletions
diff --git a/activerecord/lib/active_record/attribute_methods/primary_key.rb b/activerecord/lib/active_record/attribute_methods/primary_key.rb
index 095814b635..411330dda2 100644
--- a/activerecord/lib/active_record/attribute_methods/primary_key.rb
+++ b/activerecord/lib/active_record/attribute_methods/primary_key.rb
@@ -3,6 +3,12 @@ module ActiveRecord
     module PrimaryKey
       extend ActiveSupport::Concern
 
+      # Returns this record's primary key value wrapped in an Array
+      # or nil if the record is a new_record?
+      def to_key
+        new_record? ? nil : [ send(self.class.primary_key) ]
+      end
+
       module ClassMethods
         # Defines the primary key field -- can be overridden in subclasses. Overwriting will negate any effect of the
         # primary_key_prefix_type setting, though.
@@ -39,22 +45,6 @@ module ActiveRecord
         end
         alias :primary_key= :set_primary_key
       end
-
-      module InstanceMethods
-
-        # Returns this record's primary key value wrapped in an Array
-        # or nil if the record is a new_record?
-        # This is done to comply with the AMo interface that expects
-        # every AMo compliant object to respond_to?(:to_key) and return
-        # an Enumerable object from that call, or nil if new_record?
-        # This method also takes custom primary keys specified via
-        # the +set_primary_key+ into account.
-        def to_key
-          new_record? ? nil : [ self.primary_key ]
-        end
-
-      end
-
     end
   end
 end