diff --git a/src/main/java/com/github/nkzawa/socketio/client/On.java b/src/main/java/com/github/nkzawa/socketio/client/On.java
index 0e05f6e..c06acf9 100644
--- a/src/main/java/com/github/nkzawa/socketio/client/On.java
+++ b/src/main/java/com/github/nkzawa/socketio/client/On.java
@@ -2,11 +2,11 @@ package com.github.nkzawa.socketio.client;
 
 import com.github.nkzawa.emitter.Emitter;
 
-public class On extends Emitter {
+public class On {
 
     private On() {}
 
-    public static Handle on(final Emitter obj, final String ev, final Listener fn) {
+    public static Handle on(final Emitter obj, final String ev, final Emitter.Listener fn) {
         obj.on(ev, fn);
         return new Handle() {
             @Override