diff --git a/packages/reflection/src/TypeReflector.php b/packages/reflection/src/TypeReflector.php
index 64429ba19..acfcb0317 100644
--- a/packages/reflection/src/TypeReflector.php
+++ b/packages/reflection/src/TypeReflector.php
@@ -266,7 +266,14 @@ private function resolveDefinition(PHPReflector|PHPReflectionType|string $reflec
     private function resolveIsNullable(PHPReflectionType|PHPReflector|string $reflector): bool
     {
         if (is_string($reflector)) {
-            return str_contains($this->definition, '?') || str_contains($this->definition, 'null');
+            if (str_contains($this->definition, '?')) {
+                return true;
+            }
+
+            return array_any(
+                array: preg_split('/[&|]/', $this->definition),
+                callback: static fn (string $type) => $type === 'null',
+            );
         }
 
         if ($reflector instanceof PHPReflectionParameter || $reflector instanceof PHPReflectionProperty) {
diff --git a/packages/reflection/tests/Fixtures/AnnulledInvoice.php b/packages/reflection/tests/Fixtures/AnnulledInvoice.php
new file mode 100644
index 000000000..f5d5c7f8f
--- /dev/null
+++ b/packages/reflection/tests/Fixtures/AnnulledInvoice.php
@@ -0,0 +1,9 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Reflection\Tests\Fixtures;
+
+final readonly class AnnulledInvoice
+{
+}
diff --git a/packages/reflection/tests/Fixtures/NullableClass.php b/packages/reflection/tests/Fixtures/NullableClass.php
new file mode 100644
index 000000000..a2af1e599
--- /dev/null
+++ b/packages/reflection/tests/Fixtures/NullableClass.php
@@ -0,0 +1,9 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Reflection\Tests\Fixtures;
+
+final readonly class NullableClass
+{
+}
diff --git a/packages/reflection/tests/TypeReflectorTest.php b/packages/reflection/tests/TypeReflectorTest.php
index 623aa19be..4946c4472 100644
--- a/packages/reflection/tests/TypeReflectorTest.php
+++ b/packages/reflection/tests/TypeReflectorTest.php
@@ -4,7 +4,10 @@
 
 use PHPUnit\Framework\TestCase;
 use Tempest\Reflection\ClassReflector;
+use Tempest\Reflection\Tests\Fixtures\AnnulledInvoice;
+use Tempest\Reflection\Tests\Fixtures\NullableClass;
 use Tempest\Reflection\Tests\Fixtures\TestClassA;
+use Tempest\Reflection\TypeReflector;
 
 final class TypeReflectorTest extends TestCase
 {
@@ -90,4 +93,18 @@ public function test_is_enum(): void
                 ->isUnitEnum(),
         );
     }
+
+    public function test_is_nullable(): void
+    {
+        $this->assertTrue(new TypeReflector('?string')->isNullable());
+        $this->assertTrue(new TypeReflector('string|null')->isNullable());
+        $this->assertTrue(new TypeReflector('null')->isNullable());
+        $this->assertFalse(new TypeReflector('string')->isNullable());
+    }
+
+    public function test_class_name_containing_null_is_not_nullable(): void
+    {
+        $this->assertFalse(new TypeReflector(AnnulledInvoice::class)->isNullable());
+        $this->assertFalse(new TypeReflector(NullableClass::class)->isNullable());
+    }
 }