diff --git a/handler/src/main/java/io/netty/handler/stream/ChunkedWriteHandler.java b/handler/src/main/java/io/netty/handler/stream/ChunkedWriteHandler.java
index 2f19449fbd..b87e858a48 100644
--- a/handler/src/main/java/io/netty/handler/stream/ChunkedWriteHandler.java
+++ b/handler/src/main/java/io/netty/handler/stream/ChunkedWriteHandler.java
@@ -152,6 +152,11 @@ public class ChunkedWriteHandler
         }
     }
 
+    @Override
+    public void inboundBufferUpdated(ChannelHandlerContext ctx) throws Exception {
+        ctx.fireInboundBufferUpdated();
+    }
+
     @Override
     public void channelInactive(ChannelHandlerContext ctx) throws Exception {
         doFlush(ctx);
diff --git a/handler/src/main/java/io/netty/handler/timeout/WriteTimeoutHandler.java b/handler/src/main/java/io/netty/handler/timeout/WriteTimeoutHandler.java
index 12d3fac0d2..0be2d2522e 100644
--- a/handler/src/main/java/io/netty/handler/timeout/WriteTimeoutHandler.java
+++ b/handler/src/main/java/io/netty/handler/timeout/WriteTimeoutHandler.java
@@ -107,14 +107,12 @@ public class WriteTimeoutHandler extends ChannelOperationHandlerAdapter {
     @Override
     public void flush(final ChannelHandlerContext ctx, final ChannelPromise promise) throws Exception {
         scheduleTimeout(ctx, promise);
-
-        super.flush(ctx, promise);
+        ctx.flush(promise);
     }
 
     @Override
     public void sendFile(ChannelHandlerContext ctx, FileRegion region, ChannelPromise promise) throws Exception {
         scheduleTimeout(ctx, promise);
-
         super.sendFile(ctx, region, promise);
     }
 
diff --git a/transport/src/main/java/io/netty/channel/ChannelDuplexHandler.java b/transport/src/main/java/io/netty/channel/ChannelDuplexHandler.java
index 473ad5cde7..509c83ad6c 100644
--- a/transport/src/main/java/io/netty/channel/ChannelDuplexHandler.java
+++ b/transport/src/main/java/io/netty/channel/ChannelDuplexHandler.java
@@ -91,26 +91,6 @@ public abstract class ChannelDuplexHandler extends ChannelStateHandlerAdapter im
         ctx.read();
     }
 
-    /**
-     * Calls {@link ChannelHandlerContext#flush(ChannelPromise)} to forward
-     * to the next {@link ChannelOperationHandler} in the {@link ChannelPipeline}.
-     *
-     * Sub-classes may override this method to change behavior.
-     *
-     * Be aware that if your class also implement {@link ChannelOutboundHandler} it need to {@code @Override} this
-     * method and provide some proper implementation. Fail to do so, will result in an {@link IllegalStateException}!
-     */
-    @Override
-    public void flush(ChannelHandlerContext ctx, ChannelPromise future)
-            throws Exception {
-        if (this instanceof ChannelOutboundHandler) {
-            throw new IllegalStateException(
-                    "flush(...) must be overridden by " + getClass().getName() +
-                            ", which implements " + ChannelOutboundHandler.class.getSimpleName());
-        }
-        ctx.flush(future);
-    }
-
     /**
      * Calls {@link ChannelHandlerContext#sendFile(FileRegion, ChannelPromise)} to forward
      * to the next {@link ChannelOperationHandler} in the {@link ChannelPipeline}.
diff --git a/transport/src/main/java/io/netty/channel/ChannelInitializer.java b/transport/src/main/java/io/netty/channel/ChannelInitializer.java
index 46c913e0a8..d6516e670f 100644
--- a/transport/src/main/java/io/netty/channel/ChannelInitializer.java
+++ b/transport/src/main/java/io/netty/channel/ChannelInitializer.java
@@ -83,4 +83,9 @@ public abstract class ChannelInitializer<C extends Channel> extends ChannelState
             }
         }
     }
+
+    @Override
+    public void inboundBufferUpdated(ChannelHandlerContext ctx) throws Exception {
+        ctx.fireInboundBufferUpdated();
+    }
 }
diff --git a/transport/src/main/java/io/netty/channel/ChannelOperationHandlerAdapter.java b/transport/src/main/java/io/netty/channel/ChannelOperationHandlerAdapter.java
index a009f2123d..30dca27374 100644
--- a/transport/src/main/java/io/netty/channel/ChannelOperationHandlerAdapter.java
+++ b/transport/src/main/java/io/netty/channel/ChannelOperationHandlerAdapter.java
@@ -84,26 +84,6 @@ public abstract class ChannelOperationHandlerAdapter extends ChannelHandlerAdapt
         ctx.read();
     }
 
-    /**
-     * Calls {@link ChannelHandlerContext#flush(ChannelPromise)} to forward
-     * to the next {@link ChannelOperationHandler} in the {@link ChannelPipeline}.
-     *
-     * Sub-classes may override this method to change behavior.
-     *
-     * Be aware that if your class also implement {@link ChannelOutboundHandler} it need to {@code override} this
-     * method!
-     */
-    @Override
-    public void flush(ChannelHandlerContext ctx, ChannelPromise promise)
-            throws Exception {
-        if (this instanceof ChannelOutboundHandler) {
-            throw new IllegalStateException(
-                    "flush(...) must be overridden by " + getClass().getName() +
-                    ", which implements " + ChannelOutboundHandler.class.getSimpleName());
-        }
-        ctx.flush(promise);
-    }
-
     /**
      * Calls {@link ChannelHandlerContext#sendFile(FileRegion, ChannelPromise)} to forward
      * to the next {@link ChannelOperationHandler} in the {@link ChannelPipeline}.
diff --git a/transport/src/main/java/io/netty/channel/ChannelStateHandlerAdapter.java b/transport/src/main/java/io/netty/channel/ChannelStateHandlerAdapter.java
index 32286460e6..d0ea42d077 100644
--- a/transport/src/main/java/io/netty/channel/ChannelStateHandlerAdapter.java
+++ b/transport/src/main/java/io/netty/channel/ChannelStateHandlerAdapter.java
@@ -69,25 +69,6 @@ public abstract class ChannelStateHandlerAdapter extends ChannelHandlerAdapter i
         ctx.fireChannelInactive();
     }
 
-    /**
-     * Calls {@link ChannelHandlerContext#fireInboundBufferUpdated()} to forward
-     * to the next {@link ChannelOperationHandler} in the {@link ChannelPipeline}.
-     *
-     * Sub-classes may override this method to change behavior.
-     *
-     * Be aware that if your class also implement {@link ChannelInboundHandler} it need to {@code @Override} this
-     * method and provide some proper implementation. Fail to do so, will result in an {@link IllegalStateException}!
-     */
-    @Override
-    public void inboundBufferUpdated(ChannelHandlerContext ctx) throws Exception {
-        if (this instanceof ChannelInboundHandler) {
-            throw new IllegalStateException(
-                    "inboundBufferUpdated(...) must be overridden by " + getClass().getName() +
-                    ", which implements " + ChannelInboundHandler.class.getSimpleName());
-        }
-        ctx.fireInboundBufferUpdated();
-    }
-
     @Override
     public void channelReadSuspended(ChannelHandlerContext ctx) throws Exception {
         ctx.fireChannelReadSuspended();
diff --git a/transport/src/test/java/io/netty/channel/AbstractEventLoopTest.java b/transport/src/test/java/io/netty/channel/AbstractEventLoopTest.java
index b350d8988c..ddf9247ee6 100644
--- a/transport/src/test/java/io/netty/channel/AbstractEventLoopTest.java
+++ b/transport/src/test/java/io/netty/channel/AbstractEventLoopTest.java
@@ -60,11 +60,26 @@ public abstract class AbstractEventLoopTest {
     }
 
     private static final class TestChannelHandler extends ChannelDuplexHandler {
+        @Override
+        public void flush(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+            ctx.flush(promise);
+        }
 
+        @Override
+        public void inboundBufferUpdated(ChannelHandlerContext ctx) throws Exception {
+            ctx.fireInboundBufferUpdated();
+        }
     }
 
     private static final class TestChannelHandler2 extends ChannelDuplexHandler {
+        @Override
+        public void flush(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+            ctx.flush(promise);
+        }
 
+        @Override
+        public void inboundBufferUpdated(ChannelHandlerContext ctx) throws Exception {
+        }
     }
 
     protected abstract EventLoopGroup newEventLoopGroup();
diff --git a/transport/src/test/java/io/netty/channel/DefaultChannelPipelineTest.java b/transport/src/test/java/io/netty/channel/DefaultChannelPipelineTest.java
index 27a0606a77..f9e1eadb30 100644
--- a/transport/src/test/java/io/netty/channel/DefaultChannelPipelineTest.java
+++ b/transport/src/test/java/io/netty/channel/DefaultChannelPipelineTest.java
@@ -328,6 +328,14 @@ public class DefaultChannelPipelineTest {
 
     @Sharable
     private static class TestHandler extends ChannelDuplexHandler {
-        // Dummy
+        @Override
+        public void flush(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+            ctx.flush(promise);
+        }
+
+        @Override
+        public void inboundBufferUpdated(ChannelHandlerContext ctx) throws Exception {
+            ctx.fireInboundBufferUpdated();
+        }
     }
 }