diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index c9e18f5296d3aece83f4791cdf75b518f11bafd2..20e39e3f1b3b632434ef59ce75890de0a0ab8b1f 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -23,7 +23,8 @@ lrust:
   - coq
   script:
   - coqc -v
-  # prepare the environment
+  # prepare the environment, safeguard against outdated submodule
+  - 'git submodule status iris | egrep "^ "'
   - 'ln -s iris iris-enabled'
   # build local repo
   - 'time make -j8'