diff --git a/.travis.yml b/.travis.yml
index ac47aae..6516bbc 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,8 +1,9 @@
 language: php
 
 php:
-  - 7.0
-  
+  - 7.1
+  - 7.2
+
 cache:
   directories:
     - vendor
diff --git a/src/Instantiator/PropertyInstantiator.php b/src/Instantiator/PropertyInstantiator.php
index a4a7569..d9a1fdc 100644
--- a/src/Instantiator/PropertyInstantiator.php
+++ b/src/Instantiator/PropertyInstantiator.php
@@ -8,8 +8,12 @@
 
 class PropertyInstantiator implements InstantiatorInterface
 {
-    public function instantiate(string $class, array $data)
+    public function instantiate(string $class, ?array $data)
     {
+        if ($data === null) {
+            return null;
+        }
+
         $object = new $class();
 
         foreach ($data as $key => $value) {
diff --git a/src/Node/BaseNode.php b/src/Node/BaseNode.php
index c29c737..bde6b6c 100644
--- a/src/Node/BaseNode.php
+++ b/src/Node/BaseNode.php
@@ -225,12 +225,16 @@ public function getValue(string $field, $value)
 
     public function walk($input)
     {
-        $result = [];
+        if (!is_array($input)) {
+            return $input;
+        }
 
         if (!$this->hasChildren()) {
             return $input;
         }
 
+        $result = [];
+
         foreach ($this->getChildren() as $field => $config) {
             if (!array_key_exists($field, $input)) {
                 if ($config->isRequired()) {
diff --git a/tests/InputHandlerTest.php b/tests/InputHandlerTest.php
index dc21500..f6bb43a 100644
--- a/tests/InputHandlerTest.php
+++ b/tests/InputHandlerTest.php
@@ -99,6 +99,28 @@ public function define(): void
     }
 }
 
+class TestNullableInputHandler extends InputHandler
+{
+    public function define(): void
+    {
+        $this->add('name', 'string');
+        $this->add('address', 'string', ['allow_null' => true]);
+    }
+}
+
+class TestNullableRecursiveInputHandler extends InputHandler
+{
+    public function define(): void
+    {
+        $this->add('type', 'string');
+        $this->add('data', \stdClass::class, [
+            'handler' => new TestNullableInputHandler(),
+            'instantiator' => new PropertyInstantiator(),
+            'allow_null' => true,
+        ]);
+    }
+}
+
 class InputHandlerTest extends TestCase
 {
     public function testIsHandlingBasicInput(): void
@@ -483,6 +505,40 @@ public function testDatetimeInvalidDatetimeInput($datetime): void
         $inputHandler->bind($input);
         $this->assertFalse($inputHandler->isValid());
     }
+
+    public function testIsHandlingInputWithNullValues(): void
+    {
+        $input = [
+            'type' => 'buyers',
+            'data' => [
+                'name' => 'John Doe',
+                'address' => null,
+            ],
+        ];
+
+        $inputHandler = new TestNullableRecursiveInputHandler();
+        $inputHandler->bind($input);
+
+        $this->assertTrue($inputHandler->isValid());
+
+        $data = $inputHandler->getData('data');
+
+        $this->assertNull($data->address);
+
+        $input = [
+            'type' => 'buyers',
+            'data' => null,
+        ];
+
+        $inputHandler = new TestNullableRecursiveInputHandler();
+        $inputHandler->bind($input);
+
+        $this->assertTrue($inputHandler->isValid());
+
+        $data = $inputHandler->getData('data');
+
+        $this->assertNull($data);
+    }
 }
 
 class TestConstraintOverrideType extends InputHandler