diff --git a/.travis.yml b/.travis.yml
index e928672..d8e7d34 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,7 +1,7 @@
 language: php
 
 php:
-  - 7.1
+  - '7.1'
 
 before_script:
   - composer install --prefer-source --no-interaction