JavaScript errors when using tapx-datefield

[Lenny Primak]

I am trying to use tapx-datefield, but as soon as I declare the dependency, 
Datefield JavaScript initialization fails:

Exception invoking function Tapestry.Initializer.tapxDateField with parameters 
[{"time":false,"clientDateFormat":"%o/%e/%Y","singleClick":true,"clientId":"dateFrom"}]:
 TypeError: 'undefined' is not a function (evaluating 'Calendar.setup')
t5-console.js:73console.trace()
errort5-console.js:73
(anonymous function)tapestry.js:305
(anonymous function)tapestry.js:283
(anonymous function)tapestry.js:274
(anonymous function)prototype.js:825
t5-console.js:67Exception invoking function Tapestry.Initializer.tapxDateField 
with parameters 
[{"time":false,"clientDateFormat":"%o/%e/%Y","singleClick":true,"clientId":"dateTo"}]:
 TypeError: 'undefined' is not a function (evaluating 'Calendar.setup')
t5-console.js:73console.trace()
errort5-console.js:73
(anonymous function)tapestry.js:305
(anonymous function)tapestry.js:283
(anonymous function)tapestry.js:274
(anonymous function)

I am using Tapestry 5.3-beta-21 at the moment,
and Tapx 1.2-SNAPSHOT:

        <repository>
            <id>hls-snapshot-repo</id>
            <url>http://howardlewisship.com/snapshot-repository</url>
        </repository> 

        <dependency>
            <groupId>com.howardlewisship</groupId>
            <artifactId>tapx-datefield</artifactId>
            <version>1.2-SNAPSHOT</version>
        </dependency>

I get no other JavaScript or server-side errors.

Can anyone help me?
Thanks!