diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/HttpMessageEncoder.java b/codec-http/src/main/java/io/netty/handler/codec/http/HttpMessageEncoder.java
index e92bb38869..a4de1caecb 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/HttpMessageEncoder.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/HttpMessageEncoder.java
@@ -25,6 +25,8 @@ import io.netty.buffer.ChannelBuffer;
 import io.netty.buffer.ChannelBuffers;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelHandlerContext;
+import io.netty.handler.codec.http.HttpHeaders.Names;
+import io.netty.handler.codec.http.HttpHeaders.Values;
 import io.netty.handler.codec.oneone.OneToOneEncoder;
 import io.netty.util.CharsetUtil;
 
@@ -59,7 +61,17 @@ public abstract class HttpMessageEncoder extends OneToOneEncoder {
     protected Object encode(ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
         if (msg instanceof HttpMessage) {
             HttpMessage m = (HttpMessage) msg;
-            boolean chunked = this.chunked = HttpCodecUtil.isTransferEncodingChunked(m);
+            boolean chunked;
+            if (m.isChunked()) {
+                // check if the Transfer-Encoding is set to chunked already.
+                // if not add the header to the message
+                if (!HttpCodecUtil.isTransferEncodingChunked(m)) {
+                    m.addHeader(Names.TRANSFER_ENCODING, Values.CHUNKED);
+                }
+                chunked = this.chunked = true;
+            } else {
+                chunked = this.chunked = HttpCodecUtil.isTransferEncodingChunked(m);
+            }
             ChannelBuffer header = ChannelBuffers.dynamicBuffer(
                     channel.getConfig().getBufferFactory());
             encodeInitialLine(header, m);