TypeHandler not used for null values

Custom type handler is not called by Query* or Execute* methods for null values. In the following sample for Microsoft SQL I expect to insert DbNull value into the table if Foo.Data is null. Instead, an exception is thrown due to an invalid query parameter type (nvarchar instead of varbinary).

using Dapper;
using System;
using System.Data;
using System.Data.SqlClient;

namespace DapperBug
{
    class Program
    {
        static void Main(string[] args)
        {
            SqlMapper.AddTypeHandler(new ValuesHandler());

            var connectionString = "Data Source =.; Initial Catalog = tempdb; Integrated Security = True;";
            var sql = @"CREATE TABLE #Test (Id int IDENTITY(1,1) PRIMARY KEY, Data binary(2));
                        INSERT INTO #Test (Data) VALUES (@Data); SELECT SCOPE_IDENTITY() AS Id";
            using (var connection = new SqlConnection(connectionString))
            {
                var foo = new Foo();
                int id = connection.ExecuteScalar<int>(sql, foo);
                Console.WriteLine(id);
            }
        }
    }

    class Values
    {
        public Values() { }
        public Values(byte first, byte second)
        {
            First = first;
            Second = second;
        }

        public byte First { get; set; }
        public byte Second { get; set; }
    }

    class Foo
    {
        public int Id { get; set; }
        public Values Data { get; set; }
    }

    class ValuesHandler : SqlMapper.TypeHandler<Values>
    {
        public override Values Parse(object value)
        {
            if (value is byte[] bytes)
            {
                return new Values(bytes[0], bytes[1]);
            }

            return null;
        }

        public override void SetValue(IDbDataParameter parameter, Values value)
        {
            parameter.DbType = DbType.Binary;
            if (value == null)
            {
                parameter.Value = DBNull.Value;
            }
            else
            {
                parameter.Value = new byte[2] { value.First, value.Second };
            }
        }
    }
}

The resulting request on the server:

exec sp_executesql N'CREATE TABLE #Test (Id int IDENTITY(1,1) PRIMARY KEY, Data binary(2));
INSERT INTO #Test (Data) VALUES (@Data); SELECT SCOPE_IDENTITY() AS Id',N'@Data nvarchar(4000)',@Data=NULL

I'm trying to use a custom type handler for Systems.Drawing.Image

Start by reproducing the sample against Microsoft SQL and trace parameter handling from the Query* or Execute* methods when Foo.Data is null. Done means the custom ValuesHandler is called, the parameter is configured as binary, and the request inserts DBNull rather than using nvarchar.