How to access Yes/No field of Sharepoint List using Linq?

I have one list in which there is field with the datatype of Yes/No. I am trying to retrieve data of that field but it is giving me following error :

System.InvalidCastException: Specified cast is not valid. at Microsoft.SharePoint.Linq.SPQueryable.GetSPFieldValue[T](PropertyMap pm, DataContext dc, SPListItem item, Object entity, JoinPath joinPath) at lambda_method(ExecutionScope , SPListItem ) at System.Linq.Enumerable.WhereSelectEnumerableIterator2.MoveNext() at System.Collections.Generic.List1..ctor(IEnumerable1 collection) at System.Linq.Enumerable.ToList[TSource](IEnumerable1 source)

My query is as follows:

var query = (from san in db.San
             select san.IsDeclaredCompleted).ToList();

So can anyone suggest me what i am doing wrong?