diff --git a/lectures/02-interfaces/lecture.slide b/lectures/02-interfaces/lecture.slide
index 3b99f4f..88445fb 100644
--- a/lectures/02-interfaces/lecture.slide
+++ b/lectures/02-interfaces/lecture.slide
@@ -428,6 +428,8 @@ Check type
       return
   }
 
+  fmt.Println(a())
+
 Output:
 
   0
@@ -440,6 +442,8 @@ Output:
       }
   }
 
+  fmt.Println(b())
+
 Output:
 
   3210
@@ -489,7 +493,6 @@ Output:
       // ...parser...
   }
 
-
 * recover
 
   func main() {