diff --git a/builtin_object.go b/builtin_object.go
index a955770..d7c9272 100644
--- a/builtin_object.go
+++ b/builtin_object.go
@@ -32,6 +32,20 @@ func builtinObject_toString(call FunctionCall) Value {
 	return toValue(result)
 }
 
+func builtinObject_getPrototypeOf(call FunctionCall) Value {
+	objectValue := call.Argument(0)
+	object := objectValue._object()
+	if object == nil {
+		panic(newTypeError())
+	}
+
+	if object.prototype == nil {
+		return NullValue()
+	}
+
+	return toValue(object.prototype)
+}
+
 func builtinObject_getOwnPropertyDescriptor(call FunctionCall) Value {
 	objectValue := call.Argument(0)
 	object := objectValue._object()
diff --git a/global.go b/global.go
index 563f613..28456d9 100644
--- a/global.go
+++ b/global.go
@@ -168,6 +168,7 @@ func newContext() *_runtime {
 		},
 	)
 	self.Global.Object.write(
+		"getPrototypeOf", 1, builtinObject_getPrototypeOf,
 		"getOwnPropertyDescriptor", 2, builtinObject_getOwnPropertyDescriptor,
 		"defineProperty", 3, builtinObject_defineProperty,
 		"defineProperties", 2, builtinObject_defineProperties,
diff --git a/object_test.go b/object_test.go
index 0c6043f..f4b4f5b 100644
--- a/object_test.go
+++ b/object_test.go
@@ -23,3 +23,15 @@ func TestStringObject(t *testing.T) {
 	Is(object.get("10"), "undefined")
 	Is(object.get("2"), "z")
 }
+
+func TestObject_getPrototypeOf(t *testing.T) {
+	Terst(t)
+
+	test := runTest()
+	test(`
+        abc = {};
+        def = Object.getPrototypeOf(abc);
+        ghi = Object.getPrototypeOf(def);
+        [abc,def,ghi,ghi+""];
+    `, "[object Object],[object Object],,null")
+}
diff --git a/value.go b/value.go
index 184e17c..89c092b 100644
--- a/value.go
+++ b/value.go
@@ -250,6 +250,7 @@ func toValue_reflectValuePanic(value interface{}, kind reflect.Kind) {
 	}
 }
 
+// TODO toValue(nil)?
 func toValue(value interface{}) Value {
 	switch value := value.(type) {
 	case Value: