diff --git a/NEWS b/NEWS
index 197f59b626a..f1e3dfff6c7 100644
--- a/NEWS
+++ b/NEWS
@@ -14,6 +14,7 @@ PHP                                                                        NEWS
   . Fix empty argument cases for DOMParentNode methods. (nielsdos)
   . Fixed bug GH-11791 (Wrong default value of DOMDocument::xmlStandalone).
     (nielsdos)
+  . Fix json_encode result on DOMDocument. (nielsdos)
 
 - FFI:
   . Fix leaking definitions when using FFI::cdef()->new(...). (ilutov)
diff --git a/ext/dom/php_dom.stub.php b/ext/dom/php_dom.stub.php
index 2f26067d1ea..1c3d26cf0b0 100644
--- a/ext/dom/php_dom.stub.php
+++ b/ext/dom/php_dom.stub.php
@@ -668,7 +668,7 @@ class DOMDocument extends DOMNode implements DOMParentNode
      * @readonly
      * @deprecated
      */
-    public mixed $config = null;
+    public mixed $config;
 
     public bool $formatOutput;
 
diff --git a/ext/dom/php_dom_arginfo.h b/ext/dom/php_dom_arginfo.h
index d7c6c4496e9..f8f2e5c4b28 100644
--- a/ext/dom/php_dom_arginfo.h
+++ b/ext/dom/php_dom_arginfo.h
@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: 4570a3d2e6a74946b0f12353b1136922a2e77072 */
+ * Stub hash: 23aa0e35aff077f4a5fba1a6563bb806b3397d29 */
 
 ZEND_BEGIN_ARG_WITH_RETURN_OBJ_INFO_EX(arginfo_dom_import_simplexml, 0, 1, DOMElement, 0)
 	ZEND_ARG_TYPE_INFO(0, node, IS_OBJECT, 0)
@@ -1480,7 +1480,7 @@ static zend_class_entry *register_class_DOMDocument(zend_class_entry *class_entr
 	zend_string_release(property_documentURI_name);
 
 	zval property_config_default_value;
-	ZVAL_NULL(&property_config_default_value);
+	ZVAL_UNDEF(&property_config_default_value);
 	zend_string *property_config_name = zend_string_init("config", sizeof("config") - 1, 1);
 	zend_declare_typed_property(class_entry, property_config_name, &property_config_default_value, ZEND_ACC_PUBLIC, NULL, (zend_type) ZEND_TYPE_INIT_MASK(MAY_BE_ANY));
 	zend_string_release(property_config_name);
diff --git a/ext/dom/tests/DOMDocument_json_encode.phpt b/ext/dom/tests/DOMDocument_json_encode.phpt
new file mode 100644
index 00000000000..ed85ab4f210
--- /dev/null
+++ b/ext/dom/tests/DOMDocument_json_encode.phpt
@@ -0,0 +1,11 @@
+--TEST--
+JSON encoding a DOMDocument
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+$doc = new DOMDocument;
+echo json_encode($doc);
+?>
+--EXPECT--
+{}
diff --git a/ext/dom/tests/domobject_debug_handler.phpt b/ext/dom/tests/domobject_debug_handler.phpt
index 5966a27493f..dca787f2b6c 100644
--- a/ext/dom/tests/domobject_debug_handler.phpt
+++ b/ext/dom/tests/domobject_debug_handler.phpt
@@ -17,8 +17,6 @@ var_dump($d);
 --EXPECTF--
 Deprecated: Creation of dynamic property DOMDocument::$dynamicProperty is deprecated in %s on line %d
 object(DOMDocument)#1 (39) {
-  ["config"]=>
-  NULL
   ["dynamicProperty"]=>
   object(stdClass)#2 (0) {
   }
@@ -46,6 +44,8 @@ object(DOMDocument)#1 (39) {
   bool(true)
   ["documentURI"]=>
   string(%d) %s
+  ["config"]=>
+  NULL
   ["formatOutput"]=>
   bool(false)
   ["validateOnParse"]=>