diff --git a/composer.json b/composer.json
index dbdf27e..5af796e 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,7 @@
   },
   "require": {
     "php": ">=5.5",
-    "symfony/symfony": ">=2.6 <=3.4"
+    "symfony/symfony": ">=2.6 <4.0"
   },
   "require-dev": {
     "phpunit/phpunit": "~3.7"