Properties missing after extending CoreResultsWebPart

I've extended the CoreResultsWebPart using a new class, and have deployed it and included it in a search center page above the Core Search Results part.

At run time, the properties available in the result set for my new web part are missing all of my custom managed properties. They are available in the default core search results web part.

Is there a setting I need to configure on my web part in order to i开发者_运维知识库nclude the additional properties?

I had forgotten to set the SelectColumns property.