diff --git a/4-interface-segregation-principle.php b/4-interface-segregation-principle.php
index c988506..2206c1c 100644
--- a/4-interface-segregation-principle.php
+++ b/4-interface-segregation-principle.php
@@ -3,6 +3,7 @@
 // Interface Segregation Principle Violation
 interface Workable
 {
+    public function canCode();
     public function code();
     public function test();
 }