diff --git a/4-interface-segregation-principle.php b/4-interface-segregation-principle.php
index a1f3c66..c988506 100644
--- a/4-interface-segregation-principle.php
+++ b/4-interface-segregation-principle.php
@@ -77,7 +77,7 @@ class Programmer implements Codeable, Testable
     }
 }
 
-class Tester implements Workable
+class Tester implements Testable
 {
     public function test()
     {