diff --git a/src/Api/Client.php b/src/Api/Client.php
index 7895ab0e..12d19b6c 100644
--- a/src/Api/Client.php
+++ b/src/Api/Client.php
@@ -92,7 +92,7 @@ public function setVersion(string $version): void
      *
      * @param callable|null $function
      */
-    public function setVerifyResponse(callable $function = null): void
+    public function setVerifyResponse(?callable $function = null): void
     {
         $this->verifyResponseCallback = $function;
     }
diff --git a/src/Api/Operator.php b/src/Api/Operator.php
index a694d105..d53bb103 100644
--- a/src/Api/Operator.php
+++ b/src/Api/Operator.php
@@ -71,7 +71,7 @@ protected function deleteBy(string $field, $value, string $deleteMethodName = 'd
      *
      * @return array
      */
-    protected function getItems($structClass, $infoTag, $field = null, $value = null, callable $filter = null): array
+    protected function getItems($structClass, $infoTag, $field = null, $value = null, ?callable $filter = null): array
     {
         $packet = $this->client->getPacket();
         $getTag = $packet->addChild($this->wrapperTag)->addChild('get');
diff --git a/src/Api/Operator/Webspace.php b/src/Api/Operator/Webspace.php
index b1181106..a555b2c4 100644
--- a/src/Api/Operator/Webspace.php
+++ b/src/Api/Operator/Webspace.php
@@ -68,7 +68,7 @@ public function getLimits(string $field, $value): Struct\Limits
      *
      * @return Struct\Info
      */
-    public function create(array $properties, array $hostingProperties = null, string $planName = ''): Struct\Info
+    public function create(array $properties, ?array $hostingProperties = null, string $planName = ''): Struct\Info
     {
         $packet = $this->client->getPacket();
         $info = $packet->addChild($this->wrapperTag)->addChild('add');