diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 96bdb7ba..407d7152 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -47,6 +47,9 @@ jobs:
       - name: Run vimeo/psalm on internal code
         run: ./vendor/bin/psalm --config=psalm.xml --no-progress --shepherd --show-info=false --stats
 
+      - name: Run phpstan on internal code
+        run: ./vendor/bin/phpstan analyze -c phpstan.neon src tests
+
   tests:
     name: Tests
     runs-on: ubuntu-latest
diff --git a/composer.json b/composer.json
index 4a1266e6..6527e784 100644
--- a/composer.json
+++ b/composer.json
@@ -23,7 +23,8 @@
         "phpunit/phpunit": "^9.5",
         "vimeo/psalm": "^4.6",
         "friendsofphp/php-cs-fixer": "^2.18",
-        "symfony/var-dumper": "^5.2"
+        "symfony/var-dumper": "^5.2",
+        "phpstan/phpstan": "^0.12.88"
     },
     "autoload": {
         "psr-4": {
@@ -46,12 +47,14 @@
         ],
         "test-quality": [
             "@csrun",
-            "@psalm"
+            "@psalm",
+            "@phpstan"
         ],
         "test-unit": "./vendor/bin/phpunit --testsuite=unit",
         "test-integration": "./vendor/bin/phpunit --testsuite=integration",
         "test-coverage": "XDEBUG_MODE=coverage ./vendor/bin/phpunit --testsuite=unit,integration --coverage-html=coverage",
         "psalm": "./vendor/bin/psalm",
+        "phpstan": "./vendor/bin/phpstan analyze -c phpstan.neon src tests",
         "csfix": "./vendor/bin/php-cs-fixer fix --allow-risky=yes",
         "csrun": "./vendor/bin/php-cs-fixer fix --allow-risky=yes --dry-run"
     }
diff --git a/composer.lock b/composer.lock
index 2052a9e5..14914860 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": "405995b0e40ba2cb663ce106031ae3ce",
+    "content-hash": "bca08720d7cf241b53d2abfc0ff58205",
     "packages": [
         {
             "name": "psr/container",
@@ -2248,6 +2248,66 @@
             },
             "time": "2021-03-17T13:42:18+00:00"
         },
+        {
+            "name": "phpstan/phpstan",
+            "version": "0.12.88",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/phpstan/phpstan.git",
+                "reference": "464d1a81af49409c41074aa6640ed0c4cbd9bb68"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/phpstan/phpstan/zipball/464d1a81af49409c41074aa6640ed0c4cbd9bb68",
+                "reference": "464d1a81af49409c41074aa6640ed0c4cbd9bb68",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^7.1|^8.0"
+            },
+            "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",
+            "support": {
+                "issues": "https://github.com/phpstan/phpstan/issues",
+                "source": "https://github.com/phpstan/phpstan/tree/0.12.88"
+            },
+            "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": "2021-05-17T12:24:49+00:00"
+        },
         {
             "name": "phpunit/php-code-coverage",
             "version": "9.2.5",
diff --git a/phpstan.neon b/phpstan.neon
new file mode 100644
index 00000000..a2b3ad88
--- /dev/null
+++ b/phpstan.neon
@@ -0,0 +1,2 @@
+parameters:
+    level: 5