diff --git a/src/FluentDOM/Loader/JSONx.php b/src/FluentDOM/Loader/JSONx.php
index 3bd0eaec..2b48f3dd 100644
--- a/src/FluentDOM/Loader/JSONx.php
+++ b/src/FluentDOM/Loader/JSONx.php
@@ -15,6 +15,7 @@
   use FluentDOM\DOM\DocumentFragment;
   use FluentDOM\DOM\Element;
   use FluentDOM\Loadable;
+  use FluentDOM\Utility\Constraints;
   use FluentDOM\Utility\QualifiedName;
 
   /**
@@ -89,22 +90,12 @@ public function loadFragment($source, string $contentType, $options = []) {
      * @throws \LogicException
      */
     private function transferNode(\DOMNode $node, \DOMNode $target) {
-      if (!($node instanceof Element)) {
-        throw new \LogicException(
-          sprintf('Unexpected node type: %s', get_class($node))
-        );
-      }
-      if (
-        !(
-          $target instanceOf Element ||
-          $target instanceof DocumentFragment ||
-          $target instanceof Document
-        )
-      ) {
-        throw new \LogicException(
-          sprintf('Unexpected node type: %s', get_class($node))
-        );
-      }
+      Constraints::assertNodeClass(
+        $node, Element::class
+      );
+      Constraints::assertNodeClass(
+        $node, [Element::class, DocumentFragment::class, Document::class]
+      );
       if ($node->namespaceURI === self::XMLNS_JSONX) {
         if ($target instanceof Document) {
           $normalizedName = $name = 'json:json';
diff --git a/src/FluentDOM/Utility/Constraints.php b/src/FluentDOM/Utility/Constraints.php
index 71dc7e89..5956aab5 100644
--- a/src/FluentDOM/Utility/Constraints.php
+++ b/src/FluentDOM/Utility/Constraints.php
@@ -11,6 +11,8 @@
 
 namespace FluentDOM\Utility {
 
+  use FluentDOM\DOM\Element;
+
   /**
    * Abstract utility class that provides several constraints/validations
    */
@@ -62,6 +64,26 @@ public static function assertNode($node, $message = 'DOMNode expected, got: %s.'
       return TRUE;
     }
 
+    /**
+     * @param \DOMNode $node
+     * @param string|string[] $classes
+     * @param string $message
+     * @return boolean
+     */
+    public static function assertNodeClass(\DOMNode $node, $classes, $message = 'Unexpected node type: %s') {
+      if (!is_array($classes)) {
+        $classes = [$classes];
+      }
+      foreach ($classes as $className) {
+        if ($node instanceof $className) {
+          return TRUE;
+        }
+      }
+      throw new \LogicException(
+        sprintf($message, get_class($node))
+      );
+    }
+
     /**
      * Check if $elements is a traversable node list. It returns
      * the $elements or NULL
diff --git a/tests/FluentDOM/Utility/ConstraintsTest.php b/tests/FluentDOM/Utility/ConstraintsTest.php
index 7685c0ec..633b9015 100644
--- a/tests/FluentDOM/Utility/ConstraintsTest.php
+++ b/tests/FluentDOM/Utility/ConstraintsTest.php
@@ -1,8 +1,18 @@
 <?php
+/**
+ * FluentDOM
+ *
+ * @link https://thomas.weinert.info/FluentDOM/
+ * @copyright Copyright 2009-2019 FluentDOM Contributors
+ * @license http://www.opensource.org/licenses/mit-license.php The MIT License
+ *
+ */
+
 namespace FluentDOM\Utility {
 
   require_once __DIR__ . '/../TestCase.php';
 
+  use FluentDOM\DOM\Element;
   use FluentDOM\TestCase;
 
   class ConstraintsTest extends TestCase {
@@ -85,6 +95,53 @@ public function testAssertNodeExpectingExceptionWithModifiedMessage() {
       Constraints::assertNode(new \stdClass, 'Not a node but a %s.');
     }
 
+    /**
+     * @group Utility
+     * @group Constraints
+     * @covers \FluentDOM\Utility\Constraints::assertNodeClass
+     */
+    public function testAssertNodeClassWithMatchingClass() {
+      $document = new \DOMDocument();
+      $this->assertTrue(
+        Constraints::assertNodeClass($document, [\DOMElement::class, \DOMDocument::class])
+      );
+    }
+
+    /**
+     * @group Utility
+     * @group Constraints
+     * @covers \FluentDOM\Utility\Constraints::assertNodeClass
+     */
+    public function testAssertNodeClassExpectingException() {
+      $document = new \DOMDocument();
+      $this->expectException(\LogicException::class);
+      $this->expectExceptionMessage('Unexpected node type: DOMDocument');
+      Constraints::assertNodeClass($document, \DOMElement::class);
+    }
+
+    /**
+     * @group Utility
+     * @group Constraints
+     * @covers \FluentDOM\Utility\Constraints::assertNodeClass
+     */
+    public function testAssertNodeClassExpectingExceptionWithProvidedMessage() {
+      $document = new \DOMDocument();
+      $this->expectException(\LogicException::class);
+      $this->expectExceptionMessage('Expect DOMElement not DOMDocument');
+      Constraints::assertNodeClass($document, \DOMElement::class, 'Expect DOMElement not %s');
+    }
+
+    /**
+     * @group Utility
+     * @group Constraints
+     * @covers \FluentDOM\Utility\Constraints::assertNodeClass
+     */
+    public function testAssertNodeClassWithMultipleClassesExpectingException() {
+      $document = new \DOMDocument();
+      $this->expectException(\LogicException::class);
+      Constraints::assertNodeClass($document, [\DOMElement::class, \DOMAttr::class]);
+    }
+
 
     /**
      * @group Utility
@@ -213,4 +270,4 @@ public function testHasOptionExpectingFalse() {
       );
     }
   }
-}
\ No newline at end of file
+}