Newbie question: Calabash protests Calabash extensions

Do I need to take some action to enable Calabash's extension steps?

java -jar xmlcalabash-1.1.9-96.jar pipe.xml

<p:declare-step
    xmlns:p="http://www.w3.org/ns/xproc"
    version="1.0">
    <p:input port="source">
        <p:inline>
            <happiness />
        </p:inline>
    </p:input>
    <p:output port="result" />

    <cx:message
        xmlns:cx="http://xmlcalabash.com/ns/extensions"
        message="sadness" />
    <p:identity />
</p:declare-step>

ERROR: err:XS0044:Unexpected step name: cx:message
ERROR: It is a static error if any element in the XProc namespace or any
step has element children other than those specified for it by this
specification. In particular, the presence of atomic steps for which there
is no visible declaration may raise this error.