Option field on pages - value is not being translated to "0"

alex9

NAV 2009 SP1.
I created option field “MyOption” with the following option string: A,B,C,D,E
When I put this field on page, I noticed weird behaviour of the field. Let’s say, I have value “C” in it. I press “Delete” button and expect option “A” to appear in the field. If I move focus to another field in the same line after that, “MyOption” field appears to be blank. When I leave the line, the previous value “C” is back. At the same time, this field works as expected on the form.

It looks like blanking the option value isn't being translated to "0" on Pages. Is that known issue?