Problem with data binding to datagridview custom column

I have a problem binding data to a custom column DataGridView. I created a column that shows the rating for star-images according to the int value that it receives from the database. When I test it by adding lines manually, it works fine. But when I bind data to it, value is always null.

Here is the class code RatingColumn:

class RatingColumn : DataGridViewImageColumn
{
    public RatingColumn()
    {
        this.CellTemplate = new RatingCell();
        this.DefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter;
        this.ValueType = typeof(int);
        this.Name = "Rating";
        this.ImageLayout = DataGridViewImageCellLayout.Stretch;
    }
}

public class RatingCell : DataGridViewImageCell
{
    static Image[] starImages;

    static RatingCell()
    {
        starImages = new Image[11];

        for (int i = 0; i < 11; i++)
            starImages[i] = (Image)Properties.Resources.ResourceManager.
                GetObject("rating_" + i.ToString());
    }

    public RatingCell()
    {
        this.ValueType = typeof(int);
    }

    protected override object GetFormattedValue
         (object value, int rowIndex, ref DataGridViewCellStyle cellStyle, 
          TypeConverter valueTypeConverter, 
          TypeConverter formattedValueTypeConverter, 
          DataGridViewDataErrorContexts context)
    {
        //Here the value is always null
        return value == null ? starImages[0] : starImages[(int)value];
    }

    protected override void Paint
        (Graphics graphics, Rectangle clipBounds, Rectangle cellBounds, 
         int rowIndex, DataGridViewElementStates elementState, object value, 
         object formattedValue, string errorText, DataGridViewCellStyle cellStyle,
         DataGridViewAdvancedBorderStyle advancedBorderStyle, 
         DataGridViewPaintParts paintParts)
    {
        Image cellImage = (Image)formattedValue;
        base.Paint(graphics, clipBounds, cellBounds, rowIndex, elementState, 
          value, cellImage, errorText, cellStyle, advancedBorderStyle, 
          (paintParts & ~DataGridViewPaintParts.SelectionBackground));
    }
}

I bind data using DataProperyName

RatingColumn col = new RatingColumn();
        col.DataPropertyName = "Rating";

When I bind the same data with a DataGridViewTextBoxColumn, it works fine.