Can't create a flow-scoped service

class CardService {

   static transactional = false
   static scope = 'flow'

   long sum

   void addToSum(long i) {
      sum += i
   }
}

class CardController {

   def cardService

   def index = {
      redirect action: 'order'
   }

   def orderFlow = {
      start {
         action {
            cardService.addToSum(123)
            success()
         }
         on('success').to 'finish'
      }

      finish {}
   }
}

Error 500: Error creating bean with name 'CardController': Initialization of bean failed;
nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'cardService':
Scope 'flow' is not active for the current thread; consider defining a scoped proxy for this bean if you intend to refer to it from a singleton;
nested exception is java.lang.IllegalStateException: No request context bound to this thread; to access flow-scoped beans you must be running in a flow execution request
Servlet: grails
URI: /webfl/grails/card/index.dispatch
Exception Message: No request context bound to this thread; to access flow-scoped beans you must be running in a flow execution request

Caused by: java.lang.IllegalStateException: No request context bound to this thread; to access flow-scoped beans you must be running in a flow execution request
        at org.springframework.webflow.scope.AbstractWebFlowScope.getRequiredRequestContext(AbstractWebFlowScope.java:88)
        at org.springframework.webflow.scope.FlowScope.getScope(FlowScope.java:27)
        at org.springframework.webflow.scope.AbstractWebFlowScope.get(AbstractWebFlowScope.java:39)
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:324)