diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index a8dd19317f4fbb957eded4657241aad9de0ada65..67f2c0994157776e6e2b38070173cf73dc22608f 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -36,6 +36,7 @@ build-coq.8.13.0:
   <<: *template
   variables:
     OPAM_PINS: "coq version 8.13.0"
+    DENY_WARNINGS: "1"
 
 build-coq.8.12.2:
   <<: *template
diff --git a/Makefile.coq.local b/Makefile.coq.local
index 2e0ca1e6da3b65c94a29b4b6e8b476d4da5bcc92..e34123a3222d82f633ba4516694c9c30e581ee2d 100644
--- a/Makefile.coq.local
+++ b/Makefile.coq.local
@@ -15,7 +15,7 @@ test: $(TESTFILES:.v=.vo)
 # Make sure everything imports the options, and all Instance/Argument/Hint are qualified.
 	$(HIDE)for FILE in $(VFILES); do \
 	  if ! fgrep -q 'From iris.prelude Require Import options.' "$$FILE"; then echo "ERROR: $$FILE does not import 'options'."; echo; exit 1; fi ; \
-	  if egrep '^\s*(Instance|Arguments|Hint (Extern|Constructors|Resolve|Immediate|Mode|Opaque|Transparent|Unfold))\s' "$$FILE"; then echo "ERROR: $$FILE contains unqualified 'Instance'/'Arguments'/'Hint'."; echo; exit 1; fi \
+	  if egrep '^\s*(Instance|Arguments|Remove|Hint (Extern|Constructors|Resolve|Immediate|Mode|Opaque|Transparent|Unfold))\s' "$$FILE"; then echo "ERROR: $$FILE contains unqualified 'Instance'/'Arguments'/'Hint'."; echo; exit 1; fi \
 	done
 .PHONY: test