diff --git a/phpBB/composer.json b/phpBB/composer.json
index 3cf83a8fe9..2941293e81 100644
--- a/phpBB/composer.json
+++ b/phpBB/composer.json
@@ -1,4 +1,8 @@
 {
+	"_readme": [
+		"You MUST update the clean-vendor-dir target in build/build.xml",
+		"accordingly when adding or upgrading dependencies."
+	],
 	"minimum-stability": "beta",
 	"require": {
 		"lusitanian/oauth": "0.2.*",