diff --git a/.drone.yml b/.drone.yml
index 5b840e7..093dca2 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -22,7 +22,7 @@ steps:
 - name: run tests
   image: chialab/php
   environment:
-  - URL: testserver:8080
+  - "URL=testserver:8080"
   commands:
   - sleep 10
   - vendor/bin/phpunit tests