Solr: Omeka Categories facets

I am selecting the "tag" and "collection" fields as Facets at Solr configuration.
Some of them are compound words, and they appear split at the facets list.
I would like to keep them as compound words, is it possible?
Thanks in advance

This seems like a bug to me, but I'd need to look at it in action. Do you have a public URL for your site that I could look at?