diff --git a/handler/src/main/java/io/netty/handler/timeout/IdleStateEvent.java b/handler/src/main/java/io/netty/handler/timeout/IdleStateEvent.java
index eddd1719e3..7ec9e63d7e 100644
--- a/handler/src/main/java/io/netty/handler/timeout/IdleStateEvent.java
+++ b/handler/src/main/java/io/netty/handler/timeout/IdleStateEvent.java
@@ -16,11 +16,12 @@
 package io.netty.handler.timeout;
 
 import io.netty.channel.Channel;
+import io.netty.util.internal.ObjectUtil;
 
 /**
  * A user event triggered by {@link IdleStateHandler} when a {@link Channel} is idle.
  */
-public final class IdleStateEvent {
+public class IdleStateEvent {
     public static final IdleStateEvent FIRST_READER_IDLE_STATE_EVENT = new IdleStateEvent(IdleState.READER_IDLE, true);
     public static final IdleStateEvent READER_IDLE_STATE_EVENT = new IdleStateEvent(IdleState.READER_IDLE, false);
     public static final IdleStateEvent FIRST_WRITER_IDLE_STATE_EVENT = new IdleStateEvent(IdleState.WRITER_IDLE, true);
@@ -31,8 +32,14 @@ public final class IdleStateEvent {
     private final IdleState state;
     private final boolean first;
 
-    private IdleStateEvent(IdleState state, boolean first) {
-        this.state = state;
+    /**
+     * Constructor for sub-classes.
+     *
+     * @param state the {@link IdleStateEvent} which triggered the event.
+     * @param first {@code true} if its the first idle event for the {@link IdleStateEvent}.
+     */
+    protected IdleStateEvent(IdleState state, boolean first) {
+        this.state = ObjectUtil.checkNotNull(state, "state");
         this.first = first;
     }
 
diff --git a/handler/src/main/java/io/netty/handler/timeout/IdleStateHandler.java b/handler/src/main/java/io/netty/handler/timeout/IdleStateHandler.java
index 0c78d1fd9f..c58cd873e4 100644
--- a/handler/src/main/java/io/netty/handler/timeout/IdleStateHandler.java
+++ b/handler/src/main/java/io/netty/handler/timeout/IdleStateHandler.java
@@ -343,6 +343,22 @@ public class IdleStateHandler extends ChannelDuplexHandler {
         ctx.fireUserEventTriggered(evt);
     }
 
+    /**
+     * Returns a {@link IdleStateEvent}.
+     */
+    protected IdleStateEvent newIdleStateEvent(IdleState state, boolean first) {
+        switch (state) {
+            case ALL_IDLE:
+                return first ? IdleStateEvent.FIRST_ALL_IDLE_STATE_EVENT : IdleStateEvent.ALL_IDLE_STATE_EVENT;
+            case READER_IDLE:
+                return first ? IdleStateEvent.FIRST_READER_IDLE_STATE_EVENT : IdleStateEvent.READER_IDLE_STATE_EVENT;
+            case WRITER_IDLE:
+                return first ? IdleStateEvent.FIRST_WRITER_IDLE_STATE_EVENT : IdleStateEvent.WRITER_IDLE_STATE_EVENT;
+            default:
+                throw new Error();
+        }
+    }
+
     private final class ReaderIdleTimeoutTask implements Runnable {
 
         private final ChannelHandlerContext ctx;
@@ -367,13 +383,11 @@ public class IdleStateHandler extends ChannelDuplexHandler {
                 readerIdleTimeout =
                     ctx.executor().schedule(this, readerIdleTimeNanos, TimeUnit.NANOSECONDS);
                 try {
-                    IdleStateEvent event;
+                    IdleStateEvent event = newIdleStateEvent(IdleState.READER_IDLE, firstReaderIdleEvent);
                     if (firstReaderIdleEvent) {
                         firstReaderIdleEvent = false;
-                        event = IdleStateEvent.FIRST_READER_IDLE_STATE_EVENT;
-                    } else {
-                        event = IdleStateEvent.READER_IDLE_STATE_EVENT;
                     }
+
                     channelIdle(ctx, event);
                 } catch (Throwable t) {
                     ctx.fireExceptionCaught(t);
@@ -406,13 +420,11 @@ public class IdleStateHandler extends ChannelDuplexHandler {
                 writerIdleTimeout = ctx.executor().schedule(
                         this, writerIdleTimeNanos, TimeUnit.NANOSECONDS);
                 try {
-                    IdleStateEvent event;
+                    IdleStateEvent event = newIdleStateEvent(IdleState.WRITER_IDLE, firstWriterIdleEvent);
                     if (firstWriterIdleEvent) {
                         firstWriterIdleEvent = false;
-                        event = IdleStateEvent.FIRST_WRITER_IDLE_STATE_EVENT;
-                    } else {
-                        event = IdleStateEvent.WRITER_IDLE_STATE_EVENT;
                     }
+
                     channelIdle(ctx, event);
                 } catch (Throwable t) {
                     ctx.fireExceptionCaught(t);
@@ -448,13 +460,11 @@ public class IdleStateHandler extends ChannelDuplexHandler {
                 allIdleTimeout = ctx.executor().schedule(
                         this, allIdleTimeNanos, TimeUnit.NANOSECONDS);
                 try {
-                    IdleStateEvent event;
+                    IdleStateEvent event = newIdleStateEvent(IdleState.ALL_IDLE, firstAllIdleEvent);
                     if (firstAllIdleEvent) {
                         firstAllIdleEvent = false;
-                        event = IdleStateEvent.FIRST_ALL_IDLE_STATE_EVENT;
-                    } else {
-                        event = IdleStateEvent.ALL_IDLE_STATE_EVENT;
                     }
+
                     channelIdle(ctx, event);
                 } catch (Throwable t) {
                     ctx.fireExceptionCaught(t);