Fix compilation with Coq master.

6 jobs for master in 13 minutes and 37 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #33644
fp
build-coq.8.10.dev

00:12:25

passed #33648
fp
build-coq.8.7.2

00:05:24

passed #33647
fp
build-coq.8.8.2

00:06:27

passed #33646
fp-timing
build-coq.8.9.0

00:05:42

passed #33645
fp
build-coq.8.9.1

00:06:53

passed #33643
fp
build-coq.dev

00:13:37