diff --git a/phpBB/composer.json b/phpBB/composer.json
index 7900531cfb..4716f0770f 100644
--- a/phpBB/composer.json
+++ b/phpBB/composer.json
@@ -18,9 +18,12 @@
 		"wiki": "https://wiki.phpbb.com",
 		"irc": "irc://irc.freenode.org/phpbb"
 	},
+	"scripts": {
+		"post-update-cmd": "echo 'You MUST manually modify the clean-vendor-dir target in build/build.xml when adding or upgrading dependencies."
+	},
 	"replace": {
 		"phpbb/phpbb-core": "@self.version"
-	}
+	},
 	"require": {
 		"php": ">=5.3.3",
 		"lusitanian/oauth": "0.2.*",