diff --git a/ext/standard/tests/serialize/007.phpt b/ext/standard/tests/serialize/007.phpt
new file mode 100644
index 000000000000..2876ca1570c6
--- /dev/null
+++ b/ext/standard/tests/serialize/007.phpt
@@ -0,0 +1,38 @@
+--TEST--
+serialize() with __sleep() without props
+--FILE--
+<?php
+
+class Foo {
+    private $a = 1;
+    function __sleep() {
+        $this->a = 2;
+    }
+}
+
+class FooNull {
+    public $a = 1;
+    function __sleep() {
+        $this->a = 2;
+        return null;
+    }
+}
+
+class Bar {
+    public $a = 1;
+    function __sleep() {
+        $this->a = 2;
+        return 1;
+    }
+}
+
+var_dump(serialize(new Foo()));
+var_dump(serialize(new FooNull()));
+var_dump(serialize(new Bar()));
+?>
+--EXPECTF--
+string(31) "O:3:"Foo":1:{s:6:"%0Foo%0a";i:2;}"
+string(30) "O:7:"FooNull":1:{s:1:"a";i:2;}"
+
+Warning: serialize(): Bar::__sleep() should return an array of property names, or return null/void to delegate to default serialization in %s on line %d
+string(26) "O:3:"Bar":1:{s:1:"a";i:2;}"
diff --git a/ext/standard/tests/serialize/bug21957.phpt b/ext/standard/tests/serialize/bug21957.phpt
index 9d761a6699c9..80bc8cd66184 100644
--- a/ext/standard/tests/serialize/bug21957.phpt
+++ b/ext/standard/tests/serialize/bug21957.phpt
@@ -40,10 +40,15 @@ array(2) {
     int(2)
   }
 }
-a:2:{s:3:"one";s:3:"ABC";s:3:"two";N;}
+a:2:{s:3:"one";s:3:"ABC";s:3:"two";O:4:"test":2:{s:1:"a";i:7;s:1:"b";i:0;}}
 array(2) {
   ["one"]=>
   string(3) "ABC"
   ["two"]=>
-  NULL
+  object(test)#2 (2) {
+    ["a"]=>
+    int(7)
+    ["b"]=>
+    int(0)
+  }
 }
diff --git a/ext/standard/tests/serialize/bug79526.phpt b/ext/standard/tests/serialize/bug79526.phpt
index 440c18772d53..a7307cbcf260 100644
--- a/ext/standard/tests/serialize/bug79526.phpt
+++ b/ext/standard/tests/serialize/bug79526.phpt
@@ -24,7 +24,7 @@ serialize(new B());
 ?>
 Done
 --EXPECTF--
-Warning: serialize(): A::__sleep() should return an array only containing the names of instance-variables to serialize in %s on line %d
+Warning: serialize(): A::__sleep() should return an array of property names, or return null/void to delegate to default serialization in %s on line %d
 
 Warning: serialize(): B::__sleep() should return an array only containing the names of instance-variables to serialize in %s on line %d
 
diff --git a/ext/standard/tests/serialize/bug81163.phpt b/ext/standard/tests/serialize/bug81163.phpt
index 855fc1c953ed..fe222a10384f 100644
--- a/ext/standard/tests/serialize/bug81163.phpt
+++ b/ext/standard/tests/serialize/bug81163.phpt
@@ -18,4 +18,4 @@ class bar extends foo
 serialize(new bar());
 ?>
 --EXPECTF--
-Warning: serialize(): bar::__sleep() should return an array only containing the names of instance-variables to serialize in %s on line %d
+Warning: serialize(): bar::__sleep() should return an array of property names, or return null/void to delegate to default serialization in %s on line %d
diff --git a/ext/standard/var.c b/ext/standard/var.c
index a1ef60410a33..aeea583ad7bc 100644
--- a/ext/standard/var.c
+++ b/ext/standard/var.c
@@ -832,14 +832,14 @@ static HashTable* php_var_serialize_call_sleep(zend_object *obj, zend_function *
 	zend_call_known_instance_method(fn, obj, &retval, /* param_count */ 0, /* params */ NULL);
 	BG(serialize_lock)--;
 
-	if (Z_ISUNDEF(retval) || EG(exception)) {
+	if (Z_ISUNDEF(retval) || Z_ISNULL(retval) || EG(exception)) {
 		zval_ptr_dtor(&retval);
 		return NULL;
 	}
 
 	if (Z_TYPE(retval) != IS_ARRAY) {
 		zval_ptr_dtor(&retval);
-		php_error_docref(NULL, E_WARNING, "%s::__sleep() should return an array only containing the names of instance-variables to serialize", ZSTR_VAL(obj->ce->name));
+		php_error_docref(NULL, E_WARNING, "%s::__sleep() should return an array of property names, or return null/void to delegate to default serialization", ZSTR_VAL(obj->ce->name));
 		return NULL;
 	}
 
@@ -1215,20 +1215,18 @@ static void php_var_serialize_intern(smart_str *buf, zval *struc, php_serialize_
 						zval tmp;
 
 						ZVAL_OBJ_COPY(&tmp, Z_OBJ_P(struc));
-						if (!(ht = php_var_serialize_call_sleep(Z_OBJ(tmp), Z_FUNC_P(zv)))) {
-							if (!EG(exception)) {
-								/* we should still add element even if it's not OK,
-								 * since we already wrote the length of the array before */
-								smart_str_appendl(buf, "N;", 2);
-							}
+						ht = php_var_serialize_call_sleep(Z_OBJ(tmp), Z_FUNC_P(zv));
+						if (ht) {
+							php_var_serialize_class(buf, &tmp, ht, var_hash);
+							zend_array_release(ht);
 							OBJ_RELEASE(Z_OBJ(tmp));
 							return;
 						}
 
-						php_var_serialize_class(buf, &tmp, ht, var_hash);
-						zend_array_release(ht);
 						OBJ_RELEASE(Z_OBJ(tmp));
-						return;
+						if (EG(exception)) {
+							return;
+						}
 					}
 				}