diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 93738248a..f28e757c6 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -7,7 +7,7 @@ variables:
   STACK_ROOT: "${CI_PROJECT_DIR}/.stack"
 
 cache:
-  key: "%CI_COMMIT_REF_SLUG"
+  key: "${CI_COMMIT_REF_SLUG}"
   paths:
     - .stack
     - .stack-work