make check-system TESTS="loadable-kernel-modules-0 loadable-kernel-modules-1 loadable-kernel-modules-2" does work fine.

So I'm guessing it's another system test.  I'm running them all now.

>guix/ui.scm:1936:12: In procedure run-guix-command:
>In procedure struct-vtable: Wrong type argument in position 1 (expecting 
>struct): #f

Uhhh--we haven't changed anything there.