diff --git a/lib/active_record/session_store.rb b/lib/active_record/session_store.rb
index fde698d..9027564 100644
--- a/lib/active_record/session_store.rb
+++ b/lib/active_record/session_store.rb
@@ -7,6 +7,8 @@
 
 module ActiveRecord
   module SessionStore
+    autoload :Session, 'active_record/session_store/session'
+
     module ClassMethods # :nodoc:
       mattr_accessor :serializer
 
@@ -111,7 +113,6 @@ def self.dump(value)
 
 ActiveSupport.on_load(:active_record) do
   require 'active_record/session_store/session'
-  ActionDispatch::Session::ActiveRecordStore.session_class = ActiveRecord::SessionStore::Session
 end
 
 require 'active_record/session_store/sql_bypass'
diff --git a/lib/active_record/session_store/session.rb b/lib/active_record/session_store/session.rb
index 3fafe5e..461c6f8 100644
--- a/lib/active_record/session_store/session.rb
+++ b/lib/active_record/session_store/session.rb
@@ -103,3 +103,5 @@ def raise_on_session_data_overflow!
     end
   end
 end
+
+ActionDispatch::Session::ActiveRecordStore.session_class = ActiveRecord::SessionStore::Session