diff --git a/php_memcached.c b/php_memcached.c
index 47ed2d33..ac657521 100644
--- a/php_memcached.c
+++ b/php_memcached.c
@@ -23,6 +23,7 @@
 #include "php_memcached_private.h"
 #include "php_memcached_server.h"
 #include "g_fmt.h"
+#include "zend_interfaces.h"
 
 #include <ctype.h>
 #include <limits.h>
@@ -4412,6 +4413,10 @@ PHP_MINIT_FUNCTION(memcached)
 
 	memcached_ce = register_class_Memcached();
 	memcached_ce->create_object = php_memc_object_new;
+#if PHP_VERSION_ID < 80100
+	memcached_ce->serialize = zend_class_serialize_deny;
+	memcached_ce->unserialize = zend_class_unserialize_deny;
+#endif
 
 #ifdef HAVE_MEMCACHED_PROTOCOL
 	memcpy(&memcached_server_object_handlers, zend_get_std_object_handlers(), sizeof(zend_object_handlers));
@@ -4421,6 +4426,10 @@ PHP_MINIT_FUNCTION(memcached)
 
 	memcached_server_ce = register_class_MemcachedServer();
 	memcached_server_ce->create_object = php_memc_server_new;
+#if PHP_VERSION_ID < 80100
+	memcached_server_ce->serialize = zend_class_serialize_deny;
+	memcached_server_ce->unserialize = zend_class_unserialize_deny;
+#endif
 #endif
 
 	INIT_CLASS_ENTRY(ce, "MemcachedException", NULL);
diff --git a/php_memcached.stub.php b/php_memcached.stub.php
index 7e85ef32..2b254a3f 100644
--- a/php_memcached.stub.php
+++ b/php_memcached.stub.php
@@ -6,6 +6,7 @@
  * @generate-class-entries
  */
 
+/** @not-serializable */
 class Memcached {
 
 	public function __construct(?string $persistent_id=null, ?callable $callback=null, ?string $connection_str=null) {}
@@ -87,6 +88,7 @@ public function checkKey(string $key): bool {}
 }
 
 #if defined(HAVE_MEMCACHED_PROTOCOL)
+/** @not-serializable */
 class MemcachedServer {
 
 	public function run(string $address): bool {}
diff --git a/php_memcached_arginfo.h b/php_memcached_arginfo.h
index e8b999de..6971c5bf 100644
--- a/php_memcached_arginfo.h
+++ b/php_memcached_arginfo.h
@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: 75604abd7f58655a9ebda6f0ea579840311c1f08 */
+ * Stub hash: eb71af72c27ed853607afce6fd7519919f014217 */
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_Memcached___construct, 0, 0, 0)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, persistent_id, IS_STRING, 1, "null")
@@ -420,6 +420,9 @@ static zend_class_entry *register_class_Memcached(void)
 
 	INIT_CLASS_ENTRY(ce, "Memcached", class_Memcached_methods);
 	class_entry = zend_register_internal_class_ex(&ce, NULL);
+#if (PHP_VERSION_ID >= 80100)
+	class_entry->ce_flags |= ZEND_ACC_NOT_SERIALIZABLE;
+#endif
 #if (PHP_VERSION_ID >= 80200)
 
 #if defined(HAVE_MEMCACHED_SASL)
@@ -438,6 +441,9 @@ static zend_class_entry *register_class_MemcachedServer(void)
 
 	INIT_CLASS_ENTRY(ce, "MemcachedServer", class_MemcachedServer_methods);
 	class_entry = zend_register_internal_class_ex(&ce, NULL);
+#if (PHP_VERSION_ID >= 80100)
+	class_entry->ce_flags |= ZEND_ACC_NOT_SERIALIZABLE;
+#endif
 
 	return class_entry;
 }
diff --git a/php_memcached_legacy_arginfo.h b/php_memcached_legacy_arginfo.h
index 66d5bb91..5b3928da 100644
--- a/php_memcached_legacy_arginfo.h
+++ b/php_memcached_legacy_arginfo.h
@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: 75604abd7f58655a9ebda6f0ea579840311c1f08 */
+ * Stub hash: eb71af72c27ed853607afce6fd7519919f014217 */
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_Memcached___construct, 0, 0, 0)
 	ZEND_ARG_INFO(0, persistent_id)
@@ -416,6 +416,9 @@ static zend_class_entry *register_class_Memcached(void)
 
 	INIT_CLASS_ENTRY(ce, "Memcached", class_Memcached_methods);
 	class_entry = zend_register_internal_class_ex(&ce, NULL);
+#if (PHP_VERSION_ID >= 80100)
+	class_entry->ce_flags |= ZEND_ACC_NOT_SERIALIZABLE;
+#endif
 
 	return class_entry;
 }
@@ -427,6 +430,9 @@ static zend_class_entry *register_class_MemcachedServer(void)
 
 	INIT_CLASS_ENTRY(ce, "MemcachedServer", class_MemcachedServer_methods);
 	class_entry = zend_register_internal_class_ex(&ce, NULL);
+#if (PHP_VERSION_ID >= 80100)
+	class_entry->ce_flags |= ZEND_ACC_NOT_SERIALIZABLE;
+#endif
 
 	return class_entry;
 }
diff --git a/tests/not_serializable.phpt b/tests/not_serializable.phpt
new file mode 100644
index 00000000..f08ff22b
--- /dev/null
+++ b/tests/not_serializable.phpt
@@ -0,0 +1,23 @@
+--TEST--
+Memcached objects cannot be serialized
+--SKIPIF--
+<?php
+if (!extension_loaded("memcached")) die("skip memcached is not loaded\n");
+?>
+--FILE--
+<?php
+try {
+	serialize(new Memcached());
+} catch (Exception $e) {
+	echo $e->getMessage(), PHP_EOL;
+}
+
+try {
+	// Before PHP 8.1, only the C: format reaches the handler that throws
+	unserialize((PHP_VERSION_ID < 80100 ? 'C' : 'O') . ':9:"Memcached":0:{}');
+} catch (Exception $e) {
+	echo $e->getMessage(), PHP_EOL;
+}
+--EXPECT--
+Serialization of 'Memcached' is not allowed
+Unserialization of 'Memcached' is not allowed