ValidateSchema gives OverflowException

My table has several int(11) and int(11) nullable columns. My domain object has the same int and int? properties.

When I run ValidateSchema, I get an exception without a very good error message:

   at System.Convert.ToInt32(UInt64 value)
   at System.UInt64.System.IConvertible.ToInt32(IFormatProvider provider)
   at System.Convert.ToInt32(Object value)
   at NHibernate.Dialect.Schema.MySQLColumnMetadata..ctor(DataRow rs)
   at NHibernate.Dialect.Schema.MySQLTableMetadata.GetColumnMetadata(DataRow rs)
   at NHibernate.Dialect.Schema.AbstractTableMetadata.AddColumn(DataRow rs)
   at NHibernate.Dialect.Schema.AbstractTableMetadata.I开发者_如何转开发nitColumns(IDataBaseSchema meta)
   at NHibernate.Dialect.Schema.AbstractTableMetadata..ctor(DataRow rs, IDataBaseSchema meta, Boolean extras)
   at NHibernate.Dialect.Schema.MySQLTableMetadata..ctor(DataRow rs, IDataBaseSchema meta, Boolean extras)
   at NHibernate.Dialect.Schema.MySQLDataBaseSchema.GetTableMetadata(DataRow rs, Boolean extras)
   at NHibernate.Tool.hbm2ddl.DatabaseMetadata.GetTableMetadata(String name, String schema, String catalog, Boolean isQuoted)
   at NHibernate.Cfg.Configuration.ValidateSchema(Dialect dialect, DatabaseMetadata databaseMetadata)
   at NHibernate.Tool.hbm2ddl.SchemaValidator.Validate()

Doesn't look like the method does anything strange using reflector:

public MySQLColumnMetadata(DataRow rs) : base(rs)
{
    base.Name = Convert.ToString(rs["COLUMN_NAME"]);
    object obj2 = rs["CHARACTER_MAXIMUM_LENGTH"];
    if (obj2 != DBNull.Value)
    {
        base.ColumnSize = Convert.ToInt32(obj2);
    }
    obj2 = rs["NUMERIC_PRECISION"];
    if (obj2 != DBNull.Value)
    {
        base.NumericalPrecision = Convert.ToInt32(obj2);
    }
    base.Nullable = Convert.ToString(rs["IS_NULLABLE"]);
    base.TypeName = Convert.ToString(rs["DATA_TYPE"]);
}

I also have several DateTime and DateTime? on my model. I know nhibernate on mysql is a bit strange on DateTime's. Could this be the problem?

I added the nhibernate source, and found out it was due to a longtext column in my database. Not supported my the mysql dialect it seems.

EDIT:

And here's the fix I used to get around the issue. Don't know if it's just a workaround for my validation issue or a complete fix though...