1 files changed, 7 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/attribute_methods/primary_key.rb b/activerecord/lib/active_record/attribute_methods/primary_key.rb
index a404a5edd7..36d7f4ad11 100644
--- a/activerecord/lib/active_record/attribute_methods/primary_key.rb
+++ b/activerecord/lib/active_record/attribute_methods/primary_key.rb
@@ -14,6 +14,8 @@ module ActiveRecord
         # primary_key_prefix_type setting, though.
         def primary_key
           @primary_key ||= reset_primary_key
+          raise ActiveRecord::UnknownPrimaryKey.new(self) unless @primary_key
+          @primary_key
         end
 
         # Returns a quoted version of the primary key name, used to construct SQL statements.
@@ -29,6 +31,11 @@ module ActiveRecord
           key
         end
 
+        def primary_key? #:nodoc:
+          @primary_key ||= reset_primary_key
+          !@primary_key.nil?
+        end
+
         def get_primary_key(base_name) #:nodoc:
           return 'id' unless base_name && !base_name.blank?