diff --git a/composer.json b/composer.json
index e7048e5abe..5e40198b52 100644
--- a/composer.json
+++ b/composer.json
@@ -65,7 +65,10 @@
         "preferred-install": {
             "*": "dist"
         },
-        "sort-packages": true
+        "sort-packages": true,
+        "allow-plugins": {
+            "symfony/flex": true
+        }
     },
     "extra": {
         "branch-alias": {