diff --git a/UPGRADING b/UPGRADING
index 358e2669f..fe0ad4d10 100644
--- a/UPGRADING
+++ b/UPGRADING
@@ -41,15 +41,22 @@ it on a unix system, you need to do the following operations by hand:
    ./skins/
    ./plugins/
    ./vendor/
-4. Run `./bin/update.sh` from the commandline OR
+4a. If you previously installed plugins through composer, update dependencies
+   by running `php composer.phar update --no-dev`
+4b. Install/update dependencies using composer:
+   - get composer from https://getcomposer.org/download/
+   - rename the composer.json-dist file into composer.json
+   - if you want to use LDAP address books, enable the LDAP libraries in your
+     composer.json file by moving the items from "suggest" to the "require"
+     section (remove the explanation texts after the version!).
+   - run `php composer.phar install --no-dev`
+5. Run `./bin/update.sh` from the commandline OR
    open http://url-to-roundcube/installer/ in a browser and choose "3 Test config".
    To enable the latter one, you have to temporary set 'enable_installer'
    to true in your local config/config.inc.php file.
    WARNING: See SQLite database upgrade below.
-5. Let the update script/installer check your configuration and
+6. Let the update script/installer check your configuration and
    update your config files and database schema as suggested by the updater.
-5. If you previously installed plugins through composer, update dependencies
-   by running `php composer.phar update --no-dev`
 7. Make sure 'enable_installer' is set to false again.
 8. See Post-Upgrade Activities section.