diff --git a/config/piler-ssl.yml b/config/piler-ssl.yml
index a943015..268d2f0 100644
--- a/config/piler-ssl.yml
+++ b/config/piler-ssl.yml
@@ -26,7 +26,7 @@ services:
       - /var/run/docker.sock:/var/run/docker.sock:ro
     environment:
       - LETSENCRYPT_EMAIL=${LETSENCRYPT_EMAIL}
-      - LETSENCRYPT_TESTING=${LETSENCRYPT_TESTING:false}
+      - LETSENCRYPT_TESTING=${LETSENCRYPT_TESTING:-false}
 
   mysql:
     image: mariadb:${MARIA_DB_VERSION}