diff --git a/composer.json b/composer.json
index f0bb4ae..b542b88 100644
--- a/composer.json
+++ b/composer.json
@@ -9,7 +9,8 @@
     "phpmailer/phpmailer": "^6.1"
   },
   "require-dev": {
-    "phpunit/phpunit": "^9"
+    "phpunit/phpunit": "^9",
+    "phpstan/phpstan": "^0.12.32"
   },
   "autoload": {
     "psr-4": {
diff --git a/composer.lock b/composer.lock
index 29fb787..c4da58a 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "fb37b0b958cdf02d82468cb4596613ad",
+    "content-hash": "34563bfc619f47473b2e37a5639dd63e",
     "packages": [
         {
             "name": "phpmailer/phpmailer",
@@ -1379,6 +1379,62 @@
             ],
             "time": "2020-03-05T15:02:03+00:00"
         },
+        {
+            "name": "phpstan/phpstan",
+            "version": "0.12.32",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/phpstan/phpstan.git",
+                "reference": "d03863f504c8432b3de4d1881f73f6acb8c0e67c"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/phpstan/phpstan/zipball/d03863f504c8432b3de4d1881f73f6acb8c0e67c",
+                "reference": "d03863f504c8432b3de4d1881f73f6acb8c0e67c",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^7.1"
+            },
+            "conflict": {
+                "phpstan/phpstan-shim": "*"
+            },
+            "bin": [
+                "phpstan",
+                "phpstan.phar"
+            ],
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "0.12-dev"
+                }
+            },
+            "autoload": {
+                "files": [
+                    "bootstrap.php"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "description": "PHPStan - PHP Static Analysis Tool",
+            "funding": [
+                {
+                    "url": "https://github.com/ondrejmirtes",
+                    "type": "github"
+                },
+                {
+                    "url": "https://www.patreon.com/phpstan",
+                    "type": "patreon"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/phpstan/phpstan",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2020-07-01T11:57:52+00:00"
+        },
         {
             "name": "phpunit/php-code-coverage",
             "version": "8.0.2",