It's only necessary when checking fspecs.

I'm getting "Unable to construct gen at: ..." errors when calling (s/valid? ::my-spec my-val)

I suspect ::my-spec uses s/fspec.

the one it's erroring on currently looks like this: (s/def ::log-file #(instance? File %))

I agree with kenny, that this seems like what you'd see with s/fspec

and generally, s/valid? will not require test.check unless you are gen'ing

hmm... ok. yeah, commenting out my two fdef's eliminated it. thanks!