attrs on parent

In 6.0.3 we can do that, to hide a button from parent fields values

<field name="arch" type="xml">
    <form string="Sample">
        <field name="boolField"/>
        <field colspan="4" mode="tree" name="one2manyfield" >
            <tree>
                <fields name="field1"/>
                <fields name="field2"/>
                <button name="%(action name)d" type="action" icon="gtk-execute" attrs="{'invisible':[('boolField','!=',True)]}" />
            </tree>
        </field>
    </form>
</field>

I cant find the way to do same thing with 6.1, always got a javascript error boolfield not exist, i tried parent.boolField but still not work.

How i can do that ?

(by the way, 6.1 is so hard to debug, because form dont load and no error in browser, no error in log fields, need to open javascript monitor to find error and some time that not realy help, impossible to debug javascript with break point, because when page open, javascript is regenerate each time so break point disapear.)