diff --git a/Functions.md b/Functions.md
index 45794a8..d7f614c 100644
--- a/Functions.md
+++ b/Functions.md
@@ -55,7 +55,7 @@ exports.onShoutcut = onShoutcut;
 exports.sub_01 = sub_01;
 
 // You must explicitly specify where to find the function.
-AsyncFunction._filename = "program.js";
+AsyncFunction.__filename__ = "program.js";
 ```
 
 ## GeneratorFunction