Wix CheckBox default state

The dialog below displays a checkbox which on selected enables the Next Button. The problem is I cant get the initial state of it to be set to unchecked when the form first appears. I have tried setting the CheckBoxValue = 1 but that doesnt either work.

    <Dialog Id="DatabaseDialog" X="50" Y="50" Width="373" Height="287" Title="[ProductName]">
                <Control Id="EnableCheckBox" Property="DatabaseBackedUp" Type="CheckBox" X="20" Y="150" Width="290" Height="30" 
                         Text="Has the database been backed up?" CheckBoxValue="0" />
                <Control Id="NextButton" Type="PushButton" X="300" Y="261" Width="66" Height="18" Text="{\VSI_MS_Sans_Serif13.0_0_0}&amp;Next &gt;" TabSkip="no" Default="yes">
                    <Publish Event="EndDialog" Value="Return">DatabaseDialog_NextArgs=""</Publish>
                    <Publish Event="NewDialog" Value="[DatabaseDialog_NextArgs]">DatabaseDialog_NextArgs&lt;&gt;""</Publish>
                 <Condition Action="disable"><![CDATA[DatabaseBackedUp<> "1"]]></Condition>
                 <Condition Action="enable"><![CDATA[DatabaseBackedUp= "1"]></Condition>
                </Control>
</Dialog>