diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index b381dee8c5bcbe9e091fee49f8f3a92bfa88558f..a4bab1ee716980b46b284e9f2aa474f18031bcb6 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -31,6 +31,7 @@ build-coq.8.13.2:
   <<: *template
   variables:
     OPAM_PINS: "coq version 8.13.2"
+    DENY_WARNINGS: "1"
 
 trigger-iris.dev:
   <<: *template