Missing guidance on topfinding parallel

[dijkstracula]

Hi parallel maintainers,

Having followed the installation directions for oxcaml, I've got a fresh switch with parallel.v0.18~preview.130.55+197 installed. However, I'm not sure how to bring parallel into the toplevel; using a #require directive reports the following error:

utop # #require "parallel";;
Error: Reference to undefined compilation unit Config
Hint: This means that the interface of a module is loaded, but its implementation is not.
      Did you mean to load a compiled implementation of the module 
      using #load or by passing it as an argument to the toplevel?
─( 14:43:27 )─< command 3 >──────────────────────────────────────────────────────────────────────────{ counter: 0 }─
utop # 

I'm not fully sure how to proceed. This is the only version that seems to be available in opam, so I'm not sure how to try an earlier version:

[ntaylor@smuggo ~]$ opam show parallel

<><> parallel: information on all versions ><><><><><><><><><><><><><><><><><><>
name                   parallel
all-installed-versions v0.18~preview.130.55+197 [5.2.0+ox]
all-versions           v0.18~preview.130.55+197

A section about how to bring parallel into the top level in the documentation, if I've missed a step, would be appreciated.

Thanks,
Nathan