diff --git a/function_test.go b/function_test.go
index e4c2f62..00fac39 100644
--- a/function_test.go
+++ b/function_test.go
@@ -210,6 +210,13 @@ func TestFunction_bind(t *testing.T) {
         }
         [ ghi ];
     `, "true")
+
+	test(`
+        var abc = function (def, ghi) {};
+        var jkl = abc.bind({});
+        var mno = abc.bind({}, 1, 2);
+        [ jkl.length, mno.length ];
+    `, "2,0")
 }
 
 func TestFunction_toString(t *testing.T) {
diff --git a/type_function.go b/type_function.go
index 4203551..64d1233 100644
--- a/type_function.go
+++ b/type_function.go
@@ -38,8 +38,12 @@ func (runtime *_runtime) newBoundFunctionObject(target *_object, this Value, arg
 		call:      newBoundCallFunction(target, this, argumentList),
 		construct: defaultConstructFunction,
 	}
-	// FIXME
-	self.defineProperty("length", toValue_int(0), 0000, false)
+	length := int(toInt32(target.get("length")))
+	length -= len(argumentList)
+	if length < 0 {
+		length = 0
+	}
+	self.defineProperty("length", toValue_int(length), 0000, false)
 	return self
 }