diff --git a/composer.json b/composer.json
index 39bf56c..5448935 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,7 @@
     "php": "^7.2",
     "symfony/console": "^3.2",
     "symfony/process": "^3.2",
-    "symfony/yaml": "^3.2",
+    "symfony/yaml": "^3.2 || ^4.0",
     "gitonomy/gitlib": "~1.0",
     "psr/log": "^1",
     "knplabs/github-api": "^2.1",