diff --git a/src/Symfony/Bridge/ProxyManager/composer.json b/src/Symfony/Bridge/ProxyManager/composer.json
index 7e34cd90b5139..8cdc45cf05e48 100644
--- a/src/Symfony/Bridge/ProxyManager/composer.json
+++ b/src/Symfony/Bridge/ProxyManager/composer.json
@@ -25,6 +25,7 @@
     },
     "autoload": {
         "psr-4": { "Symfony\\Bridge\\ProxyManager\\": "" },
+        "classmap": [ "Legacy/Debug.php" ],
         "exclude-from-classmap": [
             "/Tests/"
         ]