Import: tags not importing

I’m importing from my own site’s feed into WP 3.4.2. Everything works except tags. The output from my own database looks like this:

<posttags>One, Two, Three</posttags>

I can change the code, but don’t know if there’s a configuration that will make the import work. I’ve seen older posts about tags not working, but nothing about newer versions. Does anyone know how to import tags from RSS?

Thanks!