diff --git a/src/Symfony/Component/ErrorRenderer/composer.json b/src/Symfony/Component/ErrorRenderer/composer.json
index 6966dbe72a..e253d7a860 100644
--- a/src/Symfony/Component/ErrorRenderer/composer.json
+++ b/src/Symfony/Component/ErrorRenderer/composer.json
@@ -29,6 +29,7 @@
         "symfony/http-kernel": "^4.4"
     },
     "conflict": {
+        "symfony/debug": "<5.0",
         "symfony/http-kernel": "<4.4"
     },
     "autoload": {