diff --git a/NEWS b/NEWS
index 43216c00012..761a7989b72 100644
--- a/NEWS
+++ b/NEWS
@@ -11,6 +11,7 @@ PHP                                                                        NEWS
     function triggered by bailout in php_output_lock_error()). (timwolla)
   . Fix OSS-Fuzz #471533782 (Infinite loop in GC destructor fiber). (ilutov)
   . Fix OSS-Fuzz #472563272 (Borked block_pass JMP[N]Z optimization). (ilutov)
+  . Fixed bug GH-GH-20914 (Internal enums can be cloned and compared). (Arnaud)
 
 - MbString:
   . Fixed bug GH-20833 (mb_str_pad() divide by zero if padding string is
diff --git a/Zend/tests/enum/comparison-internal.phpt b/Zend/tests/enum/comparison-internal.phpt
new file mode 100644
index 00000000000..b07c0e1dba8
--- /dev/null
+++ b/Zend/tests/enum/comparison-internal.phpt
@@ -0,0 +1,54 @@
+--TEST--
+Enum comparison (internal enum)
+--EXTENSIONS--
+zend_test
+--FILE--
+<?php
+
+$foo = ZendTestUnitEnum::Foo;
+$bar = ZendTestUnitEnum::Bar;
+
+var_dump($foo === $foo);
+var_dump($foo == $foo);
+
+var_dump($foo === $bar);
+var_dump($foo == $bar);
+
+var_dump($bar === $foo);
+var_dump($bar == $foo);
+
+var_dump($foo > $foo);
+var_dump($foo < $foo);
+var_dump($foo >= $foo);
+var_dump($foo <= $foo);
+
+var_dump($foo > $bar);
+var_dump($foo < $bar);
+var_dump($foo >= $bar);
+var_dump($foo <= $bar);
+
+var_dump($foo > true);
+var_dump($foo < true);
+var_dump($foo >= true);
+var_dump($foo <= true);
+
+?>
+--EXPECT--
+bool(true)
+bool(true)
+bool(false)
+bool(false)
+bool(false)
+bool(false)
+bool(false)
+bool(false)
+bool(true)
+bool(true)
+bool(false)
+bool(false)
+bool(false)
+bool(false)
+bool(false)
+bool(false)
+bool(true)
+bool(true)
diff --git a/Zend/tests/enum/implements-internal.phpt b/Zend/tests/enum/implements-internal.phpt
new file mode 100644
index 00000000000..518602af97e
--- /dev/null
+++ b/Zend/tests/enum/implements-internal.phpt
@@ -0,0 +1,14 @@
+--TEST--
+Enum implements (internal enum)
+--EXTENSIONS--
+zend_test
+--FILE--
+<?php
+
+var_dump(ZendTestUnitEnum::Foo instanceof _ZendTestInterface);
+var_dump(ZendTestEnumWithInterface::Foo instanceof _ZendTestInterface);
+
+?>
+--EXPECT--
+bool(false)
+bool(true)
diff --git a/Zend/tests/enum/instanceof-backed-enum.phpt b/Zend/tests/enum/instanceof-backed-enum.phpt
index 4716835d116..7087cfec74b 100644
--- a/Zend/tests/enum/instanceof-backed-enum.phpt
+++ b/Zend/tests/enum/instanceof-backed-enum.phpt
@@ -1,5 +1,7 @@
 --TEST--
 Auto implement BackedEnum interface
+--EXTENSIONS--
+zend_test
 --FILE--
 <?php
 
@@ -13,8 +15,12 @@ enum Baz: int {
 
 var_dump(Foo::Bar instanceof BackedEnum);
 var_dump(Baz::Qux instanceof BackedEnum);
+var_dump(ZendTestUnitEnum::Foo instanceof BackedEnum);
+var_dump(ZendTestIntEnum::Foo instanceof BackedEnum);
 
 ?>
 --EXPECT--
 bool(false)
 bool(true)
+bool(false)
+bool(true)
diff --git a/Zend/tests/enum/instanceof-unitenum.phpt b/Zend/tests/enum/instanceof-unitenum.phpt
index 55237963253..89b04b50466 100644
--- a/Zend/tests/enum/instanceof-unitenum.phpt
+++ b/Zend/tests/enum/instanceof-unitenum.phpt
@@ -1,5 +1,7 @@
 --TEST--
 Auto implement UnitEnum interface
+--EXTENSIONS--
+zend_test
 --FILE--
 <?php
 
@@ -11,8 +13,10 @@ class Baz {}
 
 var_dump(Foo::Bar instanceof UnitEnum);
 var_dump((new Baz()) instanceof UnitEnum);
+var_dump(ZendTestUnitEnum::Foo instanceof UnitEnum);
 
 ?>
 --EXPECT--
 bool(true)
 bool(false)
+bool(true)
diff --git a/Zend/tests/enum/no-clone-internal.phpt b/Zend/tests/enum/no-clone-internal.phpt
new file mode 100644
index 00000000000..84b7ee2634d
--- /dev/null
+++ b/Zend/tests/enum/no-clone-internal.phpt
@@ -0,0 +1,16 @@
+--TEST--
+Enum disallows cloning (internal enum)
+--EXTENSIONS--
+zend_test
+--FILE--
+<?php
+
+try {
+    var_dump(clone ZendTestIntEnum::Foo);
+} catch (Error $e) {
+    echo $e->getMessage() . "\n";
+}
+
+?>
+--EXPECT--
+Trying to clone an uncloneable object of class ZendTestIntEnum
diff --git a/Zend/tests/enum/no-dynamic-properties-internal.phpt b/Zend/tests/enum/no-dynamic-properties-internal.phpt
new file mode 100644
index 00000000000..8d821a5f629
--- /dev/null
+++ b/Zend/tests/enum/no-dynamic-properties-internal.phpt
@@ -0,0 +1,18 @@
+--TEST--
+Enum case disallows dynamic properties (internal enum)
+--EXTENSIONS--
+zend_test
+--FILE--
+<?php
+
+$bar = ZendTestUnitEnum::Bar;
+
+try {
+    $bar->baz = 'Baz';
+} catch (\Error $e) {
+    echo $e->getMessage();
+}
+
+?>
+--EXPECT--
+Cannot create dynamic property ZendTestUnitEnum::$baz
diff --git a/Zend/zend_enum.c b/Zend/zend_enum.c
index ae9e7b70121..a90e8590b02 100644
--- a/Zend/zend_enum.c
+++ b/Zend/zend_enum.c
@@ -529,6 +529,8 @@ ZEND_API zend_class_entry *zend_register_internal_enum(
 		zend_class_implements(ce, 1, zend_ce_backed_enum);
 	}
 
+	ce->default_object_handlers = &zend_enum_object_handlers;
+
 	return ce;
 }
 
diff --git a/ext/zend_test/test.c b/ext/zend_test/test.c
index bdbd2f52f0f..bcacc85caa1 100644
--- a/ext/zend_test/test.c
+++ b/ext/zend_test/test.c
@@ -72,6 +72,7 @@ static zend_class_entry *zend_test_ns2_ns_foo_class;
 static zend_class_entry *zend_test_unit_enum;
 static zend_class_entry *zend_test_string_enum;
 static zend_class_entry *zend_test_int_enum;
+static zend_class_entry *zend_test_enum_with_interface;
 static zend_class_entry *zend_test_magic_call;
 static zend_object_handlers zend_test_class_handlers;
 
@@ -1493,6 +1494,7 @@ PHP_MINIT_FUNCTION(zend_test)
 	zend_test_unit_enum = register_class_ZendTestUnitEnum();
 	zend_test_string_enum = register_class_ZendTestStringEnum();
 	zend_test_int_enum = register_class_ZendTestIntEnum();
+	zend_test_enum_with_interface = register_class_ZendTestEnumWithInterface(zend_test_interface);
 
 	zend_test_magic_call = register_class__ZendTestMagicCall();
 
diff --git a/ext/zend_test/test.stub.php b/ext/zend_test/test.stub.php
index bf9a1c6b5bc..b0fca4cc2b9 100644
--- a/ext/zend_test/test.stub.php
+++ b/ext/zend_test/test.stub.php
@@ -208,6 +208,11 @@ namespace {
         case Baz = -1;
     }
 
+    enum ZendTestEnumWithInterface implements _ZendTestInterface {
+        case Foo;
+        case Bar;
+    }
+
     function zend_trigger_bailout(): never {}
 
     function zend_test_array_return(): array {}
diff --git a/ext/zend_test/test_arginfo.h b/ext/zend_test/test_arginfo.h
index bd2240cedd6..eca1b91f6bf 100644
--- a/ext/zend_test/test_arginfo.h
+++ b/ext/zend_test/test_arginfo.h
@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: 6bccdc2444e6a68ba615fc281235a4551d0b8819 */
+ * Stub hash: b70af6d65c3d9a7242bc885d2262e0ebfee2473f */
 
 ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(arginfo_zend_trigger_bailout, 0, 0, IS_NEVER, 0)
 ZEND_END_ARG_INFO()
@@ -1261,6 +1261,20 @@ static zend_class_entry *register_class_ZendTestIntEnum(void)
 }
 #endif
 
+#if (PHP_VERSION_ID >= 80100)
+static zend_class_entry *register_class_ZendTestEnumWithInterface(zend_class_entry *class_entry__ZendTestInterface)
+{
+	zend_class_entry *class_entry = zend_register_internal_enum("ZendTestEnumWithInterface", IS_UNDEF, NULL);
+	zend_class_implements(class_entry, 1, class_entry__ZendTestInterface);
+
+	zend_enum_add_case_cstr(class_entry, "Foo", NULL);
+
+	zend_enum_add_case_cstr(class_entry, "Bar", NULL);
+
+	return class_entry;
+}
+#endif
+
 static zend_class_entry *register_class_ZendTestNS_Foo(void)
 {
 	zend_class_entry ce, *class_entry;