diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index f513d4c5b..149a890ad 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -38,6 +38,7 @@ variables:
     TZ: Europe/Brussels
     # avoid direct deprecations (using symfony phpunit bridge: https://symfony.com/doc/4.x/components/phpunit_bridge.html#internal-deprecations
     SYMFONY_DEPRECATIONS_HELPER: max[total]=99999999&max[self]=0&max[direct]=45&verbose=0
+    MAILER_DSN: 'null://null'
 
 stages:
     - Composer install