diff --git a/composer.json b/composer.json
index 388e6da04..f1d6d042f 100644
--- a/composer.json
+++ b/composer.json
@@ -98,7 +98,7 @@
         "symfony/security-bundle":      "~2.3|~3.0",
         "symfony/options-resolver":     "~2.3|~3.0",
         "symfony/form":                 "~2.3|~3.0",
-        "symfony/yaml":                 "~2.3|~3.0",
+        "symfony/yaml":                 "~2.3|~3.0|~4.0",
         "kriswallsmith/buzz":           "~0.13"
     },