[TYPO3-english] Problem with extending my extension class

[Lars Haendler]

Hi all,

I generated my extension with the kickstarter. I have this class 
extension here:

class tx_myextension_pi1 extends tslib_pibase


When I add more classes the extension these should extend my 
tx_myextension_pi1 like this:

class whatevernewclass extends tx_myextension_pi1


But when I make a new instance of my class $whateverObj = new 
whatevernewclass and use a function I get the error

Fatal error: Class 'tx_myextension_pi1' not found in 
/var/www/web42/html/typo3conf/ext/myextension/pi1/class.whatevernewclass.php


I just don't get it. Can anyone help me on this?

Thanx
Lars