diff --git a/composer.json b/composer.json
index 7b096151..245a3964 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,8 @@
         "nyholm/psr7": "^1.3.1",
         "phpunit/phpunit": "^9.3",
         "squizlabs/php_codesniffer": "^3.7",
-        "symfony/http-client": "^5.4 || ^6.3"
+        "symfony/http-client": "^5.4 || ^6.3",
+        "vimeo/psalm": "^5.25"
     },
     "suggest": {
         "nyholm/psr7": "PSR-7 message implementation",
diff --git a/src/Api/DomainV4.php b/src/Api/DomainV4.php
index affc58bf..a5c5a0f4 100644
--- a/src/Api/DomainV4.php
+++ b/src/Api/DomainV4.php
@@ -128,14 +128,10 @@ public function create(
         }
 
         if (null !== $wildcard) {
-            Assert::boolean($wildcard);
-
             $params['wildcard'] = $wildcard ? 'true' : 'false';
         }
 
         if (null !== $forceDkimAuthority) {
-            Assert::boolean($forceDkimAuthority);
-
             $params['force_dkim_authority'] = $forceDkimAuthority ? 'true' : 'false';
         }
 
@@ -174,8 +170,8 @@ public function create(
     /**
      * Removes a domain from the account.
      * WARNING: This action is irreversible! Be cautious!
-     * @param  string                                 $domain         name of the domain
-     * @param  array                                  $requestHeaders
+     * @param string $domain name of the domain
+     * @param array $requestHeaders
      * @return DeleteResponse|array|ResponseInterface
      * @throws ClientExceptionInterface
      */
@@ -451,7 +447,6 @@ public function updateUnsubscribeTracking(string $domain, string $active, string
         Assert::stringNotEmpty($active);
         Assert::oneOf($active, ['yes', 'no', 'true', 'false']);
         Assert::stringNotEmpty($htmlFooter);
-        Assert::nullOrString($textFooter);
 
         $params = [
             'active' => (in_array($active, ['yes', 'true'], true)) ? 'true' : 'false',