diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 580b05bcdc83cd21c4f0724e119600c8da8f288c..5d2e8af1b96875c4a9f2272edef2cfd686ad7bcb 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -5,6 +5,7 @@ stages:
 
 variables:
   CPU_CORES: "10"
+  OCAML: "ocaml-base-compiler.4.13.2"
 
 .only_branches: &only_branches
   only: