How do I handle soft 404s on category pages?

[ang]

I have a site that provides a service where listings are displayed on site for 30 days, then they expire. These listings are categorized by type. On occasion, categories have no listings available, and Google Webmaster Tools is listing them as Soft 404 errors. It's not possible to remove these categories and 301 redirect to another page. Any suggestions on how to work around the soft 404s?

[jesse-landry]

Can't they just go to a static "No Listings Available" page then?

[MikeRoberts]

Normally i fix soft 404 issues by redirecting or adding content to the page. So if you can't redirect then you could try adding some unique content to those pages. Basically its like they're saying the content is soooo thin or non-existent that the page looks like it 404s despite serving a 200 status.