diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index e5f3d9f47a6aacd6a5b67bf8ba3a616b6ec35a55..e802f4c1149cf883c86099a6eb6d324fe2e5735d 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -7,7 +7,7 @@ phpunit:
   needs: []
   parallel:
     matrix:
-      - PHP_VERSION: [7.4, 8.0, 8.1, 8.2]
+      - PHP_VERSION: ['7.4', '8.0', '8.1', '8.2']
   image: iras/php-composer:${PHP_VERSION}
   before_script:
     - composer install