How to configure a netty pipeline for a http proxy

I wrote a small http proxy using Netty and it has worked fine for some time now. Today I began getting strange exceptions in the log file coming from a single client:

java.lang.UnsupportedOperationException: unsupported message type: DefaultFullHttpResponse (expected: ByteBuf, FileRegion)
    at io.netty.channel.nio.AbstractNioByteChannel.filterOutboundMessage(AbstractNioByteChannel.java:276) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannel$AbstractUnsafe.write(AbstractChannel.java:654) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.DefaultChannelPipeline$HeadContext.write(DefaultChannelPipeline.java:1054) ~[netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:658) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:716) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:651) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.handler.logging.LoggingHandler.write(LoggingHandler.java:289) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:658) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:716) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:706) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:741) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.handler.codec.http.HttpObjectAggregator.decode(HttpObjectAggregator.java:131) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.handler.codec.http.HttpObjectAggregator.decode(HttpObjectAggregator.java:54) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:89) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:163) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.handler.logging.LoggingHandler.channelRead(LoggingHandler.java:283) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:787) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:130) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:511) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:468) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:382) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:354) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:137) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at java.lang.Thread.run(Thread.java:745) [na:1.7.0_79]

Looking up the source code it seems the problem occurs when sending a 100 Continue status in response to a POST request (HttpObjectAggregator lines 130-139)

if (is100ContinueExpected(m)) {
    ctx.writeAndFlush(CONTINUE).addListener(new ChannelFutureListener() {
        @Override
        public void operationComplete(ChannelFuture future) 
                throws Exception {
            if (!future.isSuccess()) {
                ctx.fireExceptionCaught(future.cause());
            }
        }
    });
}

and indeed the client causing the issue seems to be the only one sending an Expect: 100-continue header along with the request. This makes me think my handler pipeline could be setup wrong:

p.addLast(new LoggingHandler(LogLevel.DEBUG));
p.addLast(new HttpRequestDecoder());
p.addLast(new HttpObjectAggregator(MAX_CONTENT_LENGTH));
p.addLast(new HttpResponseEncoder());
p.addLast(new MyHandler(...));

The API docs for HttpObjectAggregator state that

Be aware that you need to have the HttpResponseEncoder or HttpRequestEncoder before the HttpObjectAggregator in the ChannelPipeline.

So I'm thinking both the HttpRequestDecoder and HttpResponseEncoder should precede HttpObjectAggregator in the pipeline. Could that be my problem?