diff --git a/msgpack_class.c b/msgpack_class.c
index 5e4fb4b..97fb0b0 100644
--- a/msgpack_class.c
+++ b/msgpack_class.c
@@ -1,4 +1,5 @@
 #include "php.h"
+#include "zend_interfaces.h"
 
 #include "php_msgpack.h"
 #include "msgpack_pack.h"
@@ -515,6 +516,12 @@ void msgpack_init_class() /* {{{ */ {
     INIT_CLASS_ENTRY(ce, "MessagePack", msgpack_base_methods);
     msgpack_ce = zend_register_internal_class(&ce);
     msgpack_ce->create_object = php_msgpack_base_new;
+#if PHP_VERSION_ID >= 80100
+    msgpack_ce->ce_flags |= ZEND_ACC_NOT_SERIALIZABLE;
+#else
+    msgpack_ce->serialize = zend_class_serialize_deny;
+    msgpack_ce->unserialize = zend_class_unserialize_deny;
+#endif
     memcpy(&msgpack_handlers, zend_get_std_object_handlers(),sizeof msgpack_handlers);
     msgpack_handlers.offset = offsetof(php_msgpack_base_t, object);
     msgpack_handlers.free_obj = php_msgpack_base_free;
@@ -527,6 +534,12 @@ void msgpack_init_class() /* {{{ */ {
     INIT_CLASS_ENTRY(ce, "MessagePackUnpacker", msgpack_unpacker_methods);
     msgpack_unpacker_ce = zend_register_internal_class(&ce);
     msgpack_unpacker_ce->create_object = php_msgpack_unpacker_new;
+#if PHP_VERSION_ID >= 80100
+    msgpack_unpacker_ce->ce_flags |= ZEND_ACC_NOT_SERIALIZABLE;
+#else
+    msgpack_unpacker_ce->serialize = zend_class_serialize_deny;
+    msgpack_unpacker_ce->unserialize = zend_class_unserialize_deny;
+#endif
     memcpy(&msgpack_unpacker_handlers, zend_get_std_object_handlers(),sizeof msgpack_unpacker_handlers);
     msgpack_unpacker_handlers.offset = offsetof(php_msgpack_unpacker_t, object);
     msgpack_unpacker_handlers.free_obj = php_msgpack_unpacker_free;
diff --git a/tests/144.phpt b/tests/144.phpt
new file mode 100644
index 0000000..a6f7eb3
--- /dev/null
+++ b/tests/144.phpt
@@ -0,0 +1,39 @@
+--TEST--
+MessagePack and MessagePackUnpacker cannot be serialized
+--FILE--
+<?php
+if(!extension_loaded('msgpack')) {
+    dl('msgpack.' . PHP_SHLIB_SUFFIX);
+}
+
+foreach ([new MessagePack(), new MessagePackUnpacker()] as $object) {
+    try {
+        serialize($object);
+    } catch (Exception $e) {
+        echo $e->getMessage(), PHP_EOL;
+    }
+}
+
+// Before PHP 8.1, only the C: format reaches the handler that throws
+$format = PHP_VERSION_ID < 80100 ? 'C' : 'O';
+
+foreach (['MessagePack', 'MessagePackUnpacker'] as $class) {
+    try {
+        unserialize($format . ':' . strlen($class) . ':"' . $class . '":0:{}');
+    } catch (Exception $e) {
+        echo $e->getMessage(), PHP_EOL;
+    }
+}
+
+try {
+    msgpack_pack(new MessagePack());
+} catch (Exception $e) {
+    echo $e->getMessage(), PHP_EOL;
+}
+?>
+--EXPECT--
+Serialization of 'MessagePack' is not allowed
+Serialization of 'MessagePackUnpacker' is not allowed
+Unserialization of 'MessagePack' is not allowed
+Unserialization of 'MessagePackUnpacker' is not allowed
+Serialization of 'MessagePack' is not allowed