diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index a2039cc4c60b0523be6caa5486a999bc6b17b813..e13fc633f26b485ac033fd4b4b025062b9d9d079 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -82,6 +82,7 @@ build-coq.8.12.2:
   variables:
     OPAM_PINS: "coq version 8.12.2"
     DENY_WARNINGS: "1"
+    OCAML: "ocaml-base-compiler.4.08.1"
 
 build-coq.8.11.2:
   <<: *template
@@ -89,3 +90,4 @@ build-coq.8.11.2:
   variables:
     OPAM_PINS: "coq version 8.11.2"
     DENY_WARNINGS: "1"
+    OCAML: "ocaml-base-compiler.4.08.1"