Mac "open" command opens directories with Skim, not Finder

The open command on my mac breaks when I install Skim , a PDF viewer. When I try to use open to browse a directory with Skim installed, open launches the Skim app, and I am presented with the following message: How do I make open behave properly, and open directories using Finder, like it should? It reverts back to the expected behavior when I move Skim to Trash.