diff --git a/src/controlP5/ControlKey.java b/src/controlP5/ControlKey.java
index 81f930e..409b459 100755
--- a/src/controlP5/ControlKey.java
+++ b/src/controlP5/ControlKey.java
@@ -25,7 +25,8 @@ package controlP5;
  * 
  */
 
-public interface ControlKey {
+@FunctionalInterface public interface ControlKey {
 
 	public void keyEvent();
+
 }