diff --git a/composer.json b/composer.json
index 809023b..a095617 100644
--- a/composer.json
+++ b/composer.json
@@ -10,7 +10,7 @@
     ],
     "require": {
         "php": ">=5.6",
-        "symfony/yaml": "^3.3"
+        "symfony/yaml": "^3.0 || ^4.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^5.7",