bargein prompt option in subdialog

[Pioneer]

Hi! I faced a problem. if I call vxml document from subdialog and use option bargein = true for prompt, dialog not interrupted when pressing dtmf.
The document is very simple:

<form>
        <block>
            <prompt [b]bargein="true"[/b]>
                <audio src="http://bla-bla-bla/file.wav"/>
            </prompt>
        </block>
</form>

subdialog parameters are usually:

<form>
    <subdialog name="play_file" src="playFile.vxml">
        <filled>
            <exit/>
        </filled>
    </subdialog>
</form>

Why? I need help.

[Nolecafi]

I was glad to see such information to ensure that they comply.