Fixes #449. Fix typo and missing import added
diff --git a/LanguageFeatures/Extension-methods/syntax_type_t03.dart b/LanguageFeatures/Extension-methods/syntax_type_t03.dart
index 9a80ee7..3490e4d 100644
--- a/LanguageFeatures/Extension-methods/syntax_type_t03.dart
+++ b/LanguageFeatures/Extension-methods/syntax_type_t03.dart
@@ -19,6 +19,7 @@
  * @author sgrekhov@unipro.ru
  */
 // SharedOptions=--enable-experiment=extension-methods
+import "dart:async";
 
 extension MyInt on int {}
 
@@ -30,7 +31,7 @@
 
 extension MyString on String {}
 
-extension MyString on void {}
+extension MyVoid on void {}
 
 extension MyDynamic on dynamic {}