diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index ada1ff7d4a0b59260658bac7cf076df56aeabf57..780f9ebcbe0e759b228ab856a98be950405f1833 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -47,6 +47,7 @@ build-coq.8.14.dev:
     OPAM_PINS: "coq version 8.14.dev"
     MANGLE_NAMES: "1"
     CI_COQCHK: "1"
+    DENY_WARNINGS: "1"
 
 build-coq.8.13.2:
   <<: *template
diff --git a/_CoqProject b/_CoqProject
index 77e45b94de9eec153fba2fe35d973172793159ac..6ea277df73f7bcd40ab35a6bc0b7514b9d4c6e32 100644
--- a/_CoqProject
+++ b/_CoqProject
@@ -1,4 +1,6 @@
 -Q theories stdpp
+# 'Global Hint Rewrite' not supported before Coq 8.14.
+-arg -w -arg -deprecated-hint-rewrite-without-locality
 
 theories/options.v
 theories/base.v