automapper Missing type map configuration or unsupported mapping.?

ERROR

Missing type map configuration or unsupported mapping.

Mapping types:
Cities_C391BA93C06F35100522AFBFA8F6BF3823972C9E97D5A49783829A4E90A03F00 -> IEnumerable`1
System.Data.Entity.DynamicProxies.Cities_C391BA93C06F35100522AFBFA8F6BF3823972C9E97D5A49783829A4E90A03F00 -> System.Collections.Generic.IEnumerable`1[[OsosPlus2.Core.DataAccess.Cities, OsosPlus2.Core, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]

Destination path:
CustomerViewModel.Cities.Cities

Source value:
System.Data.Entity.DynamicProxies.Cities_C391BA93C06F35100522AFBFA8F6BF3823972C9E97D5A49783829A4E90A03F00

Action Method:

public ActionResult _EditCustomer(int CustomerId)
{
    Customers customer = entity.Customers.FirstOrDefault(x => x.sno == CustomerId);
    CustomerViewModel customerViewModel = new CustomerViewModel();
    customerViewModel = AutoMapper.Mapper.Map<Customers, CustomerViewModel>(customer);

    customerViewModel.Sectors = entity.Sectors;
    customerViewModel.Cities = entity.Cities;
    customerViewModel.PowerSuppliers = entity.PowerSuppliers;

    return PartialView(customerViewModel);
}

When I fetch customer from entity, I get above error. Why only I get this error after fetching?