I'm using VFP 8, SP1 and attempting to center a checkbox in a grid column

Per the example in the help file, I have set Column.Sparse = .F. and checkbox.centered = .T. and checkbox.caption = "".

If checkbox.alignment = 0, the checkbox is always left-aligned in the column
If checkbox.alignment = 1, the checkbox is always right-aligned in the column

The checkbox is never centered in the column. Am I missing something?