diff --git a/src/Casters/GenderCast.php b/src/Casters/GenderCast.php
new file mode 100644
index 0000000..5ffeb38
--- /dev/null
+++ b/src/Casters/GenderCast.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace Zoomyboy\LaravelNami\Casters;
+
+use DateTimeInterface;
+use Spatie\LaravelData\Casts\Cast;
+use Spatie\LaravelData\Casts\Uncastable;
+use Spatie\LaravelData\Support\DataProperty;
+
+class GenderCast implements Cast
+{
+    public function cast(DataProperty $property, mixed $value, array $context): DateTimeInterface|Uncastable|null|int
+    {
+        if (23 === $value) {
+            return null;
+        }
+
+        return $value;
+    }
+}
diff --git a/src/Data/Member.php b/src/Data/Member.php
index 2df0454..27f59da 100644
--- a/src/Data/Member.php
+++ b/src/Data/Member.php
@@ -7,6 +7,7 @@ use Spatie\LaravelData\Attributes\MapInputName;
 use Spatie\LaravelData\Attributes\WithCast;
 use Spatie\LaravelData\Data;
 use Zoomyboy\LaravelNami\Casters\CarbonCast;
+use Zoomyboy\LaravelNami\Casters\GenderCast;
 use Zoomyboy\LaravelNami\Casters\StringCast;
 use Zoomyboy\LaravelNami\Tests\Factories\MemberRequestFactory;
 
@@ -39,7 +40,8 @@ class Member extends Data
         public string $email,
 
         #[MapInputName('geschlechtId')]
-        public int $genderId,
+        #[WithCast(GenderCast::class)]
+        public ?int $genderId,
 
         #[MapInputName('konfessionId')]
         public ?int $confessionId,
@@ -123,7 +125,7 @@ class Member extends Data
             'spitzname' => $this->nickname ?: '',
             'vorname' => $this->firstname ?: '',
             'nachname' => $this->lastname ?: '',
-            'geschlechtId' => $this->genderId,
+            'geschlechtId' => $this->genderId ?: 23,
             'email' => $this->email,
             'beitragsartId' => $this->feeId,
             'geburtsDatum' => $this->birthday->format('Y-m-d 00:00:00'),
diff --git a/tests/Unit/Api/FetchMemberTest.php b/tests/Unit/Api/FetchMemberTest.php
index dbdcf44..f8eaeb6 100644
--- a/tests/Unit/Api/FetchMemberTest.php
+++ b/tests/Unit/Api/FetchMemberTest.php
@@ -91,6 +91,7 @@ class FetchMemberTest extends TestCase
             'mitgliedsNummer' => null,
             'beitragsartId' => null,
             'konfessionId' => null,
+            'geschlechtId' => 23,
         ]);
 
         $member = $this->login()->member(1000, 1001);
@@ -108,6 +109,7 @@ class FetchMemberTest extends TestCase
         $this->assertNull($member->memberId);
         $this->assertNull($member->feeId);
         $this->assertNull($member->confessionId);
+        $this->assertNull($member->genderId);
     }
 
     public function testMemberFetchCanFail(): void
diff --git a/tests/Unit/Api/PutMemberTest.php b/tests/Unit/Api/PutMemberTest.php
index 58802fa..8ca1e25 100644
--- a/tests/Unit/Api/PutMemberTest.php
+++ b/tests/Unit/Api/PutMemberTest.php
@@ -138,4 +138,21 @@ class PutMemberTest extends TestCase
             'foreign' => 'fff',
         ]);
     }
+
+    public function testGenderCanBeNull(): void
+    {
+        app(MemberFake::class)
+            ->updatesSuccessfully(103, 16)
+            ->shows(103, 16, [
+                'foreign' => 'fff',
+                'kontoverbindung' => ['a' => 'b'],
+            ]);
+        $response = $this->login()->putMember(Member::factory()->inNami(103, 16)->toMember(['genderId' => null]));
+
+        $this->assertEquals(16, $response);
+
+        app(MemberFake::class)->assertUpdated(103, 16, [
+            'geschlechtId' => 23,
+        ]);
+    }
 }