"Classification cannot be changed after saving the item" error using the .Net API to update requirement

I am using Aras 11 SP15. I am trying to update a requirement I created. Here is my code:

using System;
using System.Collections.Generic;
using Aras.IOM;

namespace TestArasProject
{
    public static class Program
    {
        public static void Main(string[] args)
        {
            HttpServerConnection conn = IomFactory.CreateHttpServerConnection(serverUrl, dbName, username, password);
            Innovator inn = IomFactory.CreateInnovator(conn);
            conn.Login();

            Item updateItem = inn.newItem(requirement, "edit");
            string internalId = "FB20D91203DC4E3EB30DBA0CFBE4FD0F";
            updateItem.setAttribute("where", "[" + requirement.Replace(' ', '_') + "]." + "config_id" + " = '" + internalId + "' AND [" + requirement.Replace(' ', '_') + "]." + "is_current" + "='1'");

            // updating the name of the requirement
            updateItem.setProperty("req_rm_title", "Test Requirement" + Guid.NewGuid());

            Item result = updateItem.apply();

            Console.WriteLine(result);
            Console.WriteLine(result.isError());
            Console.ReadLine();

            conn.Logout();
       }

    }
}

I am getting the following error:

<SOAP-ENV:Envelope xmlns:SOAP-ENV="">schemas.xmlsoap.org/.../" xmlns:i18n="">www.aras.com/I18N"><SOAP-ENV:Body><SOAP-ENV:Fault>
<faultcode>1</faultcode>
<faultactor />
<faultstring>Classification cannot be changed after saving the item.</faultstring></SOAP-ENV:Fault></SOAP-ENV:Body></SOAP-ENV:Envelope>

I checked the XML which was getting created to update, this XML did not even contain the Classification property nor am I trying to update it. Here is the XML: 

<Item isNew=\"1\" isTemp=\"1\" type=\"re_Requirement\" action=\"edit\" where=\"[re_Requirement].config_id = '3AFD850B785E43F1B854EE404469FA87' AND [re_Requirement].is_current='1'\">
    <req_title>2019_06_24_12_25_42_850_-{AB}</req_title>
</Item>

I noticed that Classification (Type) is a default value on UI still I need to explicitly pass it through the API. This is not the case with Risk or Complexity type of fields. How do I update a requirement?