Cannot resolve action 'struts-default' in struts.xml

Hi,

I have 'extends="struts-default"' in my package element in struts.xml, but it results in the error 

Cannot resolve action 'struts-default' in struts.xml

I've saw another post where this error was fixed by making sure all the relevant files were grouped in the same fileset. However, by me, they are  grouped in the same fileset. 

Any ideas?