diff --git a/ext/standard/tests/serialize/bug81111.phpt b/ext/standard/tests/serialize/bug81111.phpt
new file mode 100644
index 0000000000000..e28d24f065de2
--- /dev/null
+++ b/ext/standard/tests/serialize/bug81111.phpt
@@ -0,0 +1,62 @@
+--TEST--
+Bug #81111 ()
+--FILE--
+<?php
+
+function check_serialize_throws($obj) {
+    try {
+        var_dump(serialize($obj));
+    } catch (Throwable $e) {
+        echo "Caught: " . get_class($e) . "\n";
+        echo "Message: " . $e->getMessage() . "\n";
+    }
+}
+
+function make_alias($obj) {
+    class_alias(get_class($obj), 'SomeAlias');
+    return new SomeAlias();
+}
+
+echo "Case 1: anonymous class\n";
+check_serialize_throws(new class () {});
+
+echo "\n";
+echo "Case 2: anonymous class with __serialize\n";
+check_serialize_throws(new class () {
+    public function __serialize() { return []; }
+    public function __unserialize($value) { }
+});
+
+echo "\n";
+echo "Case 3: anonymous class with Serializable\n";
+check_serialize_throws(new class () implements Serializable {
+    public function serialize() { return ''; }
+    public function unserialize(string $ser) { return new self(); }
+});
+
+echo "\n";
+echo "Case 4: aliased anonymous class with __serialize\n";
+$alias = make_alias(new class() {
+    public function __serialize() { return []; }
+});
+check_serialize_throws($alias);
+
+?>
+--EXPECTF--
+Case 1: anonymous class
+Caught: Exception
+Message: Serialization of 'class@anonymous' is not allowed
+
+Case 2: anonymous class with __serialize
+Caught: Exception
+Message: Serialization of 'class@anonymous' is not allowed
+
+Case 3: anonymous class with Serializable
+
+Deprecated: The Serializable interface is deprecated. %s
+Caught: Exception
+Message: Serialization of 'Serializable@anonymous' is not allowed
+
+Case 4: aliased anonymous class with __serialize
+Caught: Exception
+Message: Serialization of 'class@anonymous' is not allowed
diff --git a/ext/standard/var.c b/ext/standard/var.c
index 986f8236bf402..30aa030b8c0c0 100644
--- a/ext/standard/var.c
+++ b/ext/standard/var.c
@@ -23,6 +23,7 @@
 #include "php.h"
 #include "php_string.h"
 #include "php_var.h"
+#include "zend_interfaces.h"
 #include "zend_smart_str.h"
 #include "basic_functions.h"
 #include "php_incomplete_class.h"
@@ -1075,7 +1076,7 @@ static void php_var_serialize_intern(smart_str *buf, zval *struc, php_serialize_
 					return;
 				}
 
-				if (ce->__serialize) {
+				if (ce->__serialize && ce->serialize != zend_class_serialize_deny) {
 					zval retval, obj;
 					zend_string *key;
 					zval *data;