diff --git a/composer.json b/composer.json
index 19a8ed03..67eb838c 100644
--- a/composer.json
+++ b/composer.json
@@ -2,5 +2,8 @@
     "require": {
         "pug-php/pug": "^3.0",
         "mobiledetect/mobiledetectlib": "^2.8"
+    },
+    "config": {
+        "classmap-authoritative": true
     }
 }