MaskedEditExtender problem in Google Chrome: Delete and Backspace keys don't work

When I use the MaskedEditExtender on a TextBox, the delete and backspace keys don't work in Chrome.

This is my code:

<asp:TextBox ID="wsDateBox" runat="server" MaxLength="10" Style="width: 70px;"></asp:TextBox><ajaxToolkit:MaskedEditExtender ID="wsMaskedDateExtender" runat="server" TargetControlID="wsDateBox"
    Mask="99-99-9999" MaskType="None" ClearMaskOnLostFocus="false" UserDateFormat="DayMonthYear"></ajaxToolkit:MaskedEditExtender>

Am I doing something wrong?