diff --git a/composer.json b/composer.json
index 45d54d1..8c22d20 100644
--- a/composer.json
+++ b/composer.json
@@ -29,5 +29,8 @@
             "composer/installers": true,
             "wikimedia/composer-merge-plugin": false
         }
+    },
+    "require-dev": {
+        "phpstan/phpstan": "^1.10"
     }
 }
diff --git a/composer.lock b/composer.lock
index 1643481..f2a9bf7 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": "157cc1ef2fbb3b5667fd0b539ce87b27",
+    "content-hash": "c76eb19b0eb02b6a9fccb4b63f50d165",
     "packages": [
         {
             "name": "chillerlan/php-qrcode",
@@ -1545,7 +1545,70 @@
             "time": "2023-06-08T12:52:13+00:00"
         }
     ],
-    "packages-dev": [],
+    "packages-dev": [
+        {
+            "name": "phpstan/phpstan",
+            "version": "1.10.26",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/phpstan/phpstan.git",
+                "reference": "5d660cbb7e1b89253a47147ae44044f49832351f"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/phpstan/phpstan/zipball/5d660cbb7e1b89253a47147ae44044f49832351f",
+                "reference": "5d660cbb7e1b89253a47147ae44044f49832351f",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^7.2|^8.0"
+            },
+            "conflict": {
+                "phpstan/phpstan-shim": "*"
+            },
+            "bin": [
+                "phpstan",
+                "phpstan.phar"
+            ],
+            "type": "library",
+            "autoload": {
+                "files": [
+                    "bootstrap.php"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "description": "PHPStan - PHP Static Analysis Tool",
+            "keywords": [
+                "dev",
+                "static analysis"
+            ],
+            "support": {
+                "docs": "https://phpstan.org/user-guide/getting-started",
+                "forum": "https://github.com/phpstan/phpstan/discussions",
+                "issues": "https://github.com/phpstan/phpstan/issues",
+                "security": "https://github.com/phpstan/phpstan/security/policy",
+                "source": "https://github.com/phpstan/phpstan-src"
+            },
+            "funding": [
+                {
+                    "url": "https://github.com/ondrejmirtes",
+                    "type": "github"
+                },
+                {
+                    "url": "https://github.com/phpstan",
+                    "type": "github"
+                },
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/phpstan/phpstan",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2023-07-19T12:44:37+00:00"
+        }
+    ],
     "aliases": [],
     "minimum-stability": "dev",
     "stability-flags": {
diff --git a/src/ClientInfo.php b/src/ClientInfo.php
index 3ba7688..fc0b132 100644
--- a/src/ClientInfo.php
+++ b/src/ClientInfo.php
@@ -83,7 +83,7 @@ class ClientInfo implements Stringable {
         if($version < 0 || $version > self::SERIALIZE_VERSION)
             throw new RuntimeException('$data does not contain a valid version argument');
 
-        return new static(
+        return new ClientInfo(
             $data['bot'] ?? null,
             $data['client'] ?? null,
             $data['os'] ?? null,
@@ -108,7 +108,7 @@ class ClientInfo implements Stringable {
 
         $dd->parse();
 
-        return new static(
+        return new ClientInfo(
             $dd->getBot(),
             $dd->getClient(),
             $dd->getOs(),
diff --git a/src/Profile/ProfileFields.php b/src/Profile/ProfileFields.php
index aba1d5f..3269255 100644
--- a/src/Profile/ProfileFields.php
+++ b/src/Profile/ProfileFields.php
@@ -9,11 +9,9 @@ use Misuzu\DbStatementCache;
 use Misuzu\Users\User;
 
 class ProfileFields {
-    private IDbConnection $dbConn;
     private DbStatementCache $cache;
 
     public function __construct(IDbConnection $dbConn) {
-        $this->dbConn = $dbConn;
         $this->cache = new DbStatementCache($dbConn);
     }
 
@@ -210,7 +208,7 @@ class ProfileFields {
 
         foreach($fieldInfos as $key => $fieldInfo) {
             if(is_string($fieldInfo))
-                $fieldInfo = $this->getField($fieldId);
+                $fieldInfo = $this->getField($fieldInfo);
             elseif(!($fieldInfo instanceof ProfileFieldInfo))
                 throw new InvalidArgumentException('Entries of $fieldInfos must either be field IDs or instances of ProfileFieldInfo.');