diff --git a/README.md b/README.md
index b64da0f..7fb593f 100644
--- a/README.md
+++ b/README.md
@@ -133,6 +133,11 @@ quit
 
 Then edit the database configuration in /var/www/common.php and /etc/postfix/sql/alias.cf
 
+Install sodium_compat for v3 hidden_service support
+```
+cd /var/www && composer install
+```
+
 Last but not least setup the database by running
 ```
 php /var/www/setup.php
diff --git a/var/www/composer.json b/var/www/composer.json
new file mode 100644
index 0000000..0fdee2f
--- /dev/null
+++ b/var/www/composer.json
@@ -0,0 +1,5 @@
+{
+    "require": {
+        "paragonie/sodium_compat": "^1.7"
+    }
+}