<rich:calendar> loses datePattern after validation

I have a <rich:calendar> like this:

<rich:calendar enableManualInput="true" value="#{home.instance.data}" datePattern="dd/MM/yyyy">

When I enter a date like 39/19/9999, then the <rich:calendar> shows a message:

Invalid Date

Till here it's ok. The problem starts when I erase my field and try to enter a new date. It does not validate on the datePattern anymore and I can type number and letters.

How is开发者_如何学编程 this caused and how can I solve it?