diff --git a/src/Hydrator.php b/src/Hydrator.php
index d57f439..bc6d020 100644
--- a/src/Hydrator.php
+++ b/src/Hydrator.php
@@ -118,7 +118,7 @@ public function hydrate(string|object $object, array|object $data): object
                     $propertyType = $resolver->resolve(
                         $key,
                         $propertyType->getTypes(),
-                        is_array($data[$key]) ? $data[$key] : $data
+                        isset($data[$key]) && is_array($data[$key]) ? $data[$key] : $data
                     );
                 } else {
                     throw new Exception\UnsupportedPropertyTypeException(sprintf(
diff --git a/src/Resolver/EnumOrScalar.php b/src/Resolver/EnumOrScalar.php
index 7bb2129..fad2170 100644
--- a/src/Resolver/EnumOrScalar.php
+++ b/src/Resolver/EnumOrScalar.php
@@ -39,6 +39,7 @@ public function resolve(string $propertyName, array $propertyTypes, array $data)
             'integer' => 'int',
             'double'  => 'float',
             'boolean' => 'bool',
+            'NULL'    => 'null',
             default   => $valueType,
         };
 
diff --git a/tests/Fixtures/ObjectWithStringableEnumNullableUnion.php b/tests/Fixtures/ObjectWithStringableEnumNullableUnion.php
new file mode 100644
index 0000000..1c0cc05
--- /dev/null
+++ b/tests/Fixtures/ObjectWithStringableEnumNullableUnion.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace SergiX44\Hydrator\Tests\Fixtures;
+
+use SergiX44\Hydrator\Resolver\EnumOrScalar;
+
+final class ObjectWithStringableEnumNullableUnion
+{
+    #[EnumOrScalar]
+    public StringableEnum|string|null $value = null;
+}
diff --git a/tests/HydratorTest.php b/tests/HydratorTest.php
index ad27884..df47243 100644
--- a/tests/HydratorTest.php
+++ b/tests/HydratorTest.php
@@ -541,6 +541,20 @@ public function testHydrateStringableEnumUnionPropertyFloat(): void
         $this->assertSame(.23, $object->value);
     }
 
+    public function testHydrateStringableEnumUnionPropertyNull(): void
+    {
+        $object = (new Hydrator())->hydrate(Fixtures\ObjectWithStringableEnumNullableUnion::class, ['value' => null]);
+
+        $this->assertNull($object->value);
+    }
+
+    public function testHydrateStringableEnumUnionPropertyNullNonSet(): void
+    {
+        $object = (new Hydrator())->hydrate(Fixtures\ObjectWithStringableEnumNullableUnion::class, []);
+
+        $this->assertNull($object->value);
+    }
+
     public function testHydrateStringableEnumUnionPropertyBool(): void
     {
         $this->expectException(Exception\UnsupportedPropertyTypeException::class);