diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/multipart/HttpPostRequestEncoder.java b/codec-http/src/main/java/io/netty/handler/codec/http/multipart/HttpPostRequestEncoder.java
index 7a1ae253a9..41ede3403e 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/multipart/HttpPostRequestEncoder.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/multipart/HttpPostRequestEncoder.java
@@ -471,14 +471,14 @@ public class HttpPostRequestEncoder implements ChunkedMessageInput<HttpContent>
          */
         if (data instanceof Attribute) {
             if (duringMixedMode) {
-                InternalAttribute internal = new InternalAttribute();
+                InternalAttribute internal = new InternalAttribute(charset);
                 internal.addValue("\r\n--" + multipartMixedBoundary + "--");
                 multipartHttpDatas.add(internal);
                 multipartMixedBoundary = null;
                 currentFileUpload = null;
                 duringMixedMode = false;
             }
-            InternalAttribute internal = new InternalAttribute();
+            InternalAttribute internal = new InternalAttribute(charset);
             if (!multipartHttpDatas.isEmpty()) {
                 // previously a data field so CRLF
                 internal.addValue("\r\n");
@@ -503,7 +503,7 @@ public class HttpPostRequestEncoder implements ChunkedMessageInput<HttpContent>
             globalBodySize += attribute.length() + internal.size();
         } else if (data instanceof FileUpload) {
             FileUpload fileUpload = (FileUpload) data;
-            InternalAttribute internal = new InternalAttribute();
+            InternalAttribute internal = new InternalAttribute(charset);
             if (!multipartHttpDatas.isEmpty()) {
                 // previously a data field so CRLF
                 internal.addValue("\r\n");
@@ -525,7 +525,7 @@ public class HttpPostRequestEncoder implements ChunkedMessageInput<HttpContent>
                     multipartMixedBoundary = null;
                     // start a new one (could be replaced if mixed start again
                     // from here
-                    internal = new InternalAttribute();
+                    internal = new InternalAttribute(charset);
                     internal.addValue("\r\n");
                     localMixed = false;
                     // new currentFileUpload and no more in Mixed mode
@@ -640,7 +640,7 @@ public class HttpPostRequestEncoder implements ChunkedMessageInput<HttpContent>
         // Finalize the multipartHttpDatas
         if (!headerFinalized) {
             if (isMultipart) {
-                InternalAttribute internal = new InternalAttribute();
+                InternalAttribute internal = new InternalAttribute(charset);
                 if (duringMixedMode) {
                     internal.addValue("\r\n--" + multipartMixedBoundary + "--");
                 }
@@ -799,14 +799,7 @@ public class HttpPostRequestEncoder implements ChunkedMessageInput<HttpContent>
         }
         ByteBuf buffer;
         if (currentData instanceof InternalAttribute) {
-            String internal = currentData.toString();
-            byte[] bytes;
-            try {
-                bytes = internal.getBytes("ASCII");
-            } catch (UnsupportedEncodingException e) {
-                throw new ErrorDataEncoderException(e);
-            }
-            buffer = wrappedBuffer(bytes);
+            buffer = ((InternalAttribute) currentData).toByteBuf();
             currentData = null;
         } else {
             if (currentData instanceof Attribute) {
diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/multipart/InternalAttribute.java b/codec-http/src/main/java/io/netty/handler/codec/http/multipart/InternalAttribute.java
index e929fb7c4b..2a83f1985f 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/multipart/InternalAttribute.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/multipart/InternalAttribute.java
@@ -15,6 +15,10 @@
  */
 package io.netty.handler.codec.http.multipart;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
+
+import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -23,36 +27,46 @@ import java.util.List;
  * (like Multipart Mixed mode)
  */
 final class InternalAttribute implements InterfaceHttpData {
-    private final List<String> value = new ArrayList<String>();
+    private final List<ByteBuf> value = new ArrayList<ByteBuf>();
+    private final Charset charset;
+    private int size;
+    public InternalAttribute(Charset charset) {
+        this.charset = charset;
+    }
 
     @Override
     public HttpDataType getHttpDataType() {
         return HttpDataType.InternalAttribute;
     }
 
-    public List<String> getValue() {
-        return value;
-    }
-
     public void addValue(String value) {
         if (value == null) {
             throw new NullPointerException("value");
         }
-        this.value.add(value);
+        ByteBuf buf = Unpooled.copiedBuffer(value, charset);
+        this.value.add(buf);
+        size += buf.readableBytes();
     }
 
     public void addValue(String value, int rank) {
         if (value == null) {
             throw new NullPointerException("value");
         }
-        this.value.add(rank, value);
+        ByteBuf buf = Unpooled.copiedBuffer(value, charset);
+        this.value.add(rank, buf);
+        size += buf.readableBytes();
     }
 
     public void setValue(String value, int rank) {
         if (value == null) {
             throw new NullPointerException("value");
         }
-        this.value.set(rank, value);
+        ByteBuf buf = Unpooled.copiedBuffer(value, charset);
+        ByteBuf old = this.value.set(rank, buf);
+        if (old != null) {
+            size -= old.readableBytes();
+        }
+        size += buf.readableBytes();
     }
 
     @Override
@@ -82,22 +96,23 @@ final class InternalAttribute implements InterfaceHttpData {
         return getName().compareToIgnoreCase(o.getName());
     }
 
-    public int size() {
-        int size = 0;
-        for (String elt : value) {
-            size += elt.length();
-        }
-        return size;
-    }
     @Override
     public String toString() {
         StringBuilder result = new StringBuilder();
-        for (String elt : value) {
-            result.append(elt);
+        for (ByteBuf elt : value) {
+            result.append(elt.toString(charset));
         }
         return result.toString();
     }
 
+    public int size() {
+        return size;
+    }
+
+    public ByteBuf toByteBuf() {
+        return Unpooled.compositeBuffer().addComponents(value).writerIndex(size()).readerIndex(0);
+    }
+
     @Override
     public String getName() {
         return "InternalAttribute";