diff --git a/src/OrderDocument.php b/src/OrderDocument.php
index 923cf45..c68aa0b 100644
--- a/src/OrderDocument.php
+++ b/src/OrderDocument.php
@@ -57,7 +57,7 @@ class OrderDocument
 
     /**
      * @internal
-     * @return \horstoeko\orderx\entities\basic\rsm\SCRDMCCBDACIOMessageStructure|\horstoeko\orderx\entities\comfort\rsm\SCRDMCCBDACIOMessageStructure|\horstoeko\orderx\entities\extended\rsm\SCRDMCCBDACIOMessageStructure
+     * @return   \horstoeko\orderx\entities\basic\rsm\SCRDMCCBDACIOMessageStructure|\horstoeko\orderx\entities\comfort\rsm\SCRDMCCBDACIOMessageStructure|\horstoeko\orderx\entities\extended\rsm\SCRDMCCBDACIOMessageStructure
      */
     private $orderObject = null;
 
@@ -86,7 +86,7 @@ final protected function __construct(int $profile)
      *
      * @return \horstoeko\orderx\entities\basic\rsm\SCRDMCCBDACIOMessageStructure|\horstoeko\orderx\entities\comfort\rsm\SCRDMCCBDACIOMessageStructure|\horstoeko\orderx\entities\extended\rsm\SCRDMCCBDACIOMessageStructure
      */
-    public function getOrderObject()
+    protected function getOrderObject()
     {
         return $this->orderObject;
     }
@@ -108,7 +108,7 @@ protected function createOrderObject()
      *
      * @return SerializerInterface
      */
-    public function getSerializer()
+    protected function getSerializer()
     {
         return $this->serializer;
     }
@@ -118,7 +118,7 @@ public function getSerializer()
      *
      * @return OrderObjectHelper
      */
-    public function getObjectHelper()
+    protected function getObjectHelper()
     {
         return $this->objectHelper;
     }
diff --git a/src/OrderDocumentValidator.php b/src/OrderDocumentValidator.php
index e8f80f8..2945597 100644
--- a/src/OrderDocumentValidator.php
+++ b/src/OrderDocumentValidator.php
@@ -57,7 +57,7 @@ public function __construct(OrderDocument $document)
      */
     public function validateDocument(): ConstraintViolationListInterface
     {
-        return $this->validator->validate($this->document->getOrderObject(), null, ['xsd_rules']);
+        return $this->validator->validate($this->getDocumentOrderObject(), null, ['xsd_rules']);
     }
 
     /**
@@ -103,4 +103,19 @@ private function globRecursive(string $pattern, int $flags = 0): array
 
         return $files;
     }
+
+    /**
+     * Returns the internal invoice object from the document
+     *
+     * @return object
+     */
+    private function getDocumentOrderObject()
+    {
+        $reflector = new \ReflectionClass($this->document);
+
+        $method = $reflector->getMethod('getOrderObject');
+        $method->setAccessible(true);
+
+        return $method->invoke($this->document);
+    }
 }
diff --git a/tests/TestCase.php b/tests/TestCase.php
index 266e7eb..64ffa48 100644
--- a/tests/TestCase.php
+++ b/tests/TestCase.php
@@ -190,6 +190,20 @@ public function getPrivateMethodFromObject(object $object, string $methodName):
         return $method;
     }
 
+    /**
+     * Access to private method and invoke it
+     *
+     * @param  object $object
+     * @param  string $methodName
+     * @param  array  $args
+     * @return mixed
+     */
+    public function invokePivateMethodFromObject($object, string $methodName, ...$args)
+    {
+        $method = $this->getPrivateMethodFromObject($object, $methodName);
+        return $method->invoke($object, ...$args);
+    }
+
     /**
      * Create a dummy DateTime instance
      *
diff --git a/tests/testcases/OrderDocumentBuilderBasicTest.php b/tests/testcases/OrderDocumentBuilderBasicTest.php
index da1e2cd..477fa0f 100644
--- a/tests/testcases/OrderDocumentBuilderBasicTest.php
+++ b/tests/testcases/OrderDocumentBuilderBasicTest.php
@@ -26,7 +26,8 @@ public function testDocumentProperties(): void
     {
         (self::$document)->initNewDocument();
 
-        $this->assertNotNull(self::$document->getOrderObject());
+        $this->assertNotNull($this->invokePivateMethodFromObject(self::$document, 'getOrderObject'));
+        $this->assertEquals('horstoeko\orderx\entities\basic\rsm\SCRDMCCBDACIOMessageStructure', get_class($this->invokePivateMethodFromObject(self::$document, 'getOrderObject')));
         $property = $this->getPrivatePropertyFromObject(self::$document, 'headerTradeAgreement');
         $this->assertNotNull($property->getValue(self::$document));
         $property = $this->getPrivatePropertyFromObject(self::$document, 'headerTradeDelivery');
diff --git a/tests/testcases/OrderDocumentBuilderComfortTest.php b/tests/testcases/OrderDocumentBuilderComfortTest.php
index 3fd9478..f72d63a 100644
--- a/tests/testcases/OrderDocumentBuilderComfortTest.php
+++ b/tests/testcases/OrderDocumentBuilderComfortTest.php
@@ -26,7 +26,8 @@ public function testDocumentProperties(): void
     {
         (self::$document)->initNewDocument();
 
-        $this->assertNotNull(self::$document->getOrderObject());
+        $this->assertNotNull($this->invokePivateMethodFromObject(self::$document, 'getOrderObject'));
+        $this->assertEquals('horstoeko\orderx\entities\comfort\rsm\SCRDMCCBDACIOMessageStructure', get_class($this->invokePivateMethodFromObject(self::$document, 'getOrderObject')));
         $property = $this->getPrivatePropertyFromObject(self::$document, 'headerTradeAgreement');
         $this->assertNotNull($property->getValue(self::$document));
         $property = $this->getPrivatePropertyFromObject(self::$document, 'headerTradeDelivery');
diff --git a/tests/testcases/OrderDocumentBuilderExtendedTest.php b/tests/testcases/OrderDocumentBuilderExtendedTest.php
index 18a342d..7479ef4 100644
--- a/tests/testcases/OrderDocumentBuilderExtendedTest.php
+++ b/tests/testcases/OrderDocumentBuilderExtendedTest.php
@@ -26,7 +26,8 @@ public function testDocumentProperties(): void
     {
         (self::$document)->initNewDocument();
 
-        $this->assertNotNull(self::$document->getOrderObject());
+        $this->assertNotNull($this->invokePivateMethodFromObject(self::$document, 'getOrderObject'));
+        $this->assertEquals('horstoeko\orderx\entities\extended\rsm\SCRDMCCBDACIOMessageStructure', get_class($this->invokePivateMethodFromObject(self::$document, 'getOrderObject')));
         $property = $this->getPrivatePropertyFromObject(self::$document, 'headerTradeAgreement');
         $this->assertNotNull($property->getValue(self::$document));
         $property = $this->getPrivatePropertyFromObject(self::$document, 'headerTradeDelivery');
diff --git a/tests/testcases/OrderDocumentPdfReaderComfortTest.php b/tests/testcases/OrderDocumentPdfReaderComfortTest.php
index 9b8bfca..d37e3fa 100644
--- a/tests/testcases/OrderDocumentPdfReaderComfortTest.php
+++ b/tests/testcases/OrderDocumentPdfReaderComfortTest.php
@@ -35,7 +35,8 @@ public function testPdfRead(): void
 
     public function testDocumentProperties(): void
     {
-        $this->assertNotNull(self::$document->getOrderObject());
+        $this->assertNotNull($this->invokePivateMethodFromObject(self::$document, 'getOrderObject'));
+        $this->assertEquals('horstoeko\orderx\entities\comfort\rsm\SCRDMCCBDACIOMessageStructure', get_class($this->invokePivateMethodFromObject(self::$document, 'getOrderObject')));
     }
 
     public function testDocumentProfile(): void
diff --git a/tests/testcases/OrderDocumentPdfReaderExtendedTest.php b/tests/testcases/OrderDocumentPdfReaderExtendedTest.php
index 8668c55..aaa09ee 100644
--- a/tests/testcases/OrderDocumentPdfReaderExtendedTest.php
+++ b/tests/testcases/OrderDocumentPdfReaderExtendedTest.php
@@ -35,7 +35,8 @@ public function testPdfRead(): void
 
     public function testDocumentProperties(): void
     {
-        $this->assertNotNull(self::$document->getOrderObject());
+        $this->assertNotNull($this->invokePivateMethodFromObject(self::$document, 'getOrderObject'));
+        $this->assertEquals('horstoeko\orderx\entities\extended\rsm\SCRDMCCBDACIOMessageStructure', get_class($this->invokePivateMethodFromObject(self::$document, 'getOrderObject')));
     }
 
     public function testDocumentProfile(): void
diff --git a/tests/testcases/OrderDocumentReaderComfortTest.php b/tests/testcases/OrderDocumentReaderComfortTest.php
index 3376c30..4376159 100644
--- a/tests/testcases/OrderDocumentReaderComfortTest.php
+++ b/tests/testcases/OrderDocumentReaderComfortTest.php
@@ -26,7 +26,8 @@ public static function setUpBeforeClass(): void
 
     public function testDocumentProperties(): void
     {
-        $this->assertNotNull(self::$document->getOrderObject());
+        $this->assertNotNull($this->invokePivateMethodFromObject(self::$document, 'getOrderObject'));
+        $this->assertEquals('horstoeko\orderx\entities\comfort\rsm\SCRDMCCBDACIOMessageStructure', get_class($this->invokePivateMethodFromObject(self::$document, 'getOrderObject')));
     }
 
     public function testDocumentProfile(): void
diff --git a/tests/testcases/OrderDocumentReaderExtendedTest.php b/tests/testcases/OrderDocumentReaderExtendedTest.php
index 32ab51c..c0cd1d2 100644
--- a/tests/testcases/OrderDocumentReaderExtendedTest.php
+++ b/tests/testcases/OrderDocumentReaderExtendedTest.php
@@ -26,7 +26,8 @@ public static function setUpBeforeClass(): void
 
     public function testDocumentProperties(): void
     {
-        $this->assertNotNull(self::$document->getOrderObject());
+        $this->assertNotNull($this->invokePivateMethodFromObject(self::$document, 'getOrderObject'));
+        $this->assertEquals('horstoeko\orderx\entities\extended\rsm\SCRDMCCBDACIOMessageStructure', get_class($this->invokePivateMethodFromObject(self::$document, 'getOrderObject')));
     }
 
     public function testDocumentProfile(): void