diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/HttpCodecUtil.java b/codec-http/src/main/java/io/netty/handler/codec/http/HttpCodecUtil.java
index ac40046505..d2a7b1dc00 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/HttpCodecUtil.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/HttpCodecUtil.java
@@ -151,6 +151,17 @@ final class HttpCodecUtil {
         return false;
     }
 
+    static void removeTransferEncodingChunked(HttpMessage m) {
+        List<String> values = m.getHeaders(HttpHeaders.Names.TRANSFER_ENCODING);
+        values.remove(HttpHeaders.Values.CHUNKED);
+        m.setHeader(HttpHeaders.Names.TRANSFER_ENCODING, values);
+    }
+
+    static boolean isContentLengthSet(HttpMessage m) {
+        List<String> contentLength = m.getHeaders(HttpHeaders.Names.CONTENT_LENGTH);
+        return !contentLength.isEmpty();
+    }
+
     /**
      * A constructor to ensure that instances of this class are never made
      */
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 c83c192190..ca84a0ee16 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
@@ -47,7 +47,7 @@ public abstract class HttpMessageEncoder extends MessageToByteEncoder<Object> {
     private static final ByteBuf LAST_CHUNK =
         copiedBuffer("0\r\n\r\n", CharsetUtil.US_ASCII);
 
-    private volatile boolean chunked;
+    private boolean transferEncodingChunked;
 
     /**
      * Creates a new instance.
@@ -64,17 +64,25 @@ public abstract class HttpMessageEncoder extends MessageToByteEncoder<Object> {
     public void encode(ChannelHandlerContext ctx, Object msg, ByteBuf out) throws Exception {
         if (msg instanceof HttpMessage) {
             HttpMessage m = (HttpMessage) msg;
-            boolean chunked;
+            boolean contentMustBeEmmpty;
             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);
+                // if Content-Length is set then the message can't be HTTP chunked
+                if (HttpCodecUtil.isContentLengthSet(m)) {
+                    contentMustBeEmmpty = false;
+                    transferEncodingChunked = false;
+                } else {
+                    // 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);
+                    }
+                    contentMustBeEmmpty = true;
+                    transferEncodingChunked = true;
                 }
-                chunked = this.chunked = true;
             } else {
-                chunked = this.chunked = HttpCodecUtil.isTransferEncodingChunked(m);
+                transferEncodingChunked = contentMustBeEmmpty = HttpCodecUtil.isTransferEncodingChunked(m);
             }
+
             out.markWriterIndex();
             encodeInitialLine(out, m);
             encodeHeaders(out, m);
@@ -83,20 +91,19 @@ public abstract class HttpMessageEncoder extends MessageToByteEncoder<Object> {
 
             ByteBuf content = m.getContent();
             if (content.readable()) {
-                if (chunked) {
+                if (contentMustBeEmmpty) {
                     out.resetWriterIndex();
                     throw new IllegalArgumentException(
-                            "HttpMessage.content must be empty " +
-                            "if Transfer-Encoding is chunked.");
+                            "HttpMessage.content must be empty if Transfer-Encoding is chunked.");
                 } else {
                     out.writeBytes(content, content.readerIndex(), content.readableBytes());
                 }
             }
         } else if (msg instanceof HttpChunk) {
             HttpChunk chunk = (HttpChunk) msg;
-            if (chunked) {
+            if (transferEncodingChunked) {
                 if (chunk.isLast()) {
-                    chunked = false;
+                    transferEncodingChunked = false;
                     if (chunk instanceof HttpChunkTrailer) {
                         out.writeByte((byte) '0');
                         out.writeByte(CR);