[Seaside] Having one problem with WACounter tutorial

[Ryan Bell]

My image is squeak-dev-72-2.image

When I'm trying to change the links in the counter to buttons (as
specified in the tutorial), I get this error:

MessageNotUnderstood: WARenderCanvas>>submitButtonWithAction:text:

Here's the code cut and pasted from the tutorial:

renderContentOn: html
    html form:  [
       html heading: count.
       html submitButtonWithAction: [self increase] text: '++'.
       html space.
       html submitButtonWithAction: [self decrease] text: '--'
     ].

Can anyone tell me what I am missing?
-- 
Ryan L. Bell
http://kofno.wordpress.com
http://kofno.blogger.com