1 files changed, 3 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
index b888148841..5fbd79d118 100644
--- a/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
+++ b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
@@ -76,6 +76,9 @@ module ActiveRecord::Associations::Builder # :nodoc:
           left_model.retrieve_connection
         end
 
+        def self.primary_key
+          false
+        end
       }
 
       join_model.name                = "HABTM_#{association_name.to_s.camelize}"