diff --git a/composer.json b/composer.json
index 76db734..4b52178 100644
--- a/composer.json
+++ b/composer.json
@@ -19,8 +19,8 @@
 
     "require": {
         "php":                      ">=5.3.9",
-        "symfony/framework-bundle": "~2.3|~3.0",
-        "symfony/dependency-injection": "~2.3|~3.0",
+        "symfony/framework-bundle": "~2.3|~3.0|^4.0",
+        "symfony/dependency-injection": "~2.3|~3.0|^4.0",
         "michelf/php-markdown":     "~1.4"
     },
     "require-dev": {