diff --git a/composer.json b/composer.json
index 9cadd53..3ba99cb 100644
--- a/composer.json
+++ b/composer.json
@@ -17,7 +17,7 @@
   ],
   "require": {
     "php": ">=5.4.0",
-    "symfony/yaml": "^3.1"
+    "symfony/yaml": ">=2.7 <=4.0"
   },
   "require-dev": {
     "phpunit/phpunit": "<5.0",