diff --git a/composer.json b/composer.json
index c98fe6ba..5d13a96b 100644
--- a/composer.json
+++ b/composer.json
@@ -32,7 +32,8 @@
     "nikic/php-parser": "^v5.5.0",
     "ext-inotify": "*",
     "game-worker/kiri-pool": "^v1.0",
-    "psr/container": "^2.0"
+    "psr/container": "^2.0",
+    "swiftmailer/swiftmailer": "^v6.3.0"
   },
   "replace": {
     "symfony/polyfill-apcu": "*",