Newly added OutArgument to Activity is not visible in Workflow designer

Hi, 

I have an existing workflow and code activity. 

I have added a new OutArgument to Activity as below and deployed the Activities on CRM  after updting the version number.

        [Output("Web Url")]
        public OutArgument<string> WebUrl { get; set; }

I can't see the new Parameter in Workflow designer. It still show the older Out Parameters but newly added parameter is not there. I have already tried IISRESET. Please suggest me if I am missing anything. 

Thanks in advance