Textbox text selection in draggable row unavailable in Firefox

<zk>
    <grid>
        <columns sizable="true">
            <column label="label" width="50px"/>
            <column label="textbox"/>
        </columns>
        <rows>
            <row draggable="true">
                <label value="test"/>
                <textbox value="test text" width="99%"/>
            </row>
        </rows>
    </grid>
</zk>