diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/multipart/AbstractDiskHttpData.java b/codec-http/src/main/java/io/netty/handler/codec/http/multipart/AbstractDiskHttpData.java
index 3eac4ff99d..0844a613a4 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/multipart/AbstractDiskHttpData.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/multipart/AbstractDiskHttpData.java
@@ -156,7 +156,6 @@ public abstract class AbstractDiskHttpData extends AbstractHttpData {
                     throw new IOException("Out of size: " + (size + localsize) +
                             " > " + definedSize);
                 }
-                int written = 0;
                 if (file == null) {
                     file = tempFile();
                 }
@@ -164,9 +163,21 @@ public abstract class AbstractDiskHttpData extends AbstractHttpData {
                     RandomAccessFile accessFile = new RandomAccessFile(file, "rw");
                     fileChannel = accessFile.getChannel();
                 }
-                buffer.getBytes(buffer.readerIndex(), fileChannel, fileChannel.position(), localsize);
+                int totalWritten = 0;
+                long position = fileChannel.position();
+                int index = buffer.readerIndex();
+                while (totalWritten < localsize) {
+                    int written = buffer.getBytes(index, fileChannel, position, localsize - totalWritten);
+                    if (written < 0) {
+                        break;
+                    }
+                    totalWritten += written;
+                    position += written;
+                    index += written;
+                }
+                fileChannel.position(position);
+                buffer.readerIndex(index);
                 size += localsize;
-                buffer.readerIndex(buffer.readerIndex() + written);
             } finally {
                 // Release the buffer as it was retained before and we not need a reference to it at all
                 // See https://github.com/netty/netty/issues/1516
diff --git a/codec-http/src/test/java/io/netty/handler/codec/http/multipart/DiskFileUploadTest.java b/codec-http/src/test/java/io/netty/handler/codec/http/multipart/DiskFileUploadTest.java
index 8fd665dbb4..49ad2d62f2 100644
--- a/codec-http/src/test/java/io/netty/handler/codec/http/multipart/DiskFileUploadTest.java
+++ b/codec-http/src/test/java/io/netty/handler/codec/http/multipart/DiskFileUploadTest.java
@@ -113,16 +113,19 @@ public class DiskFileUploadTest {
     public void testAddContents() throws Exception {
         DiskFileUpload f1 = new DiskFileUpload("file1", "file1", "application/json", null, null, 0);
         try {
-            String json = "{\"foo\":\"bar\"}";
-            byte[] bytes = json.getBytes(CharsetUtil.UTF_8);
-            f1.addContent(Unpooled.wrappedBuffer(bytes), true);
-            assertEquals(json, f1.getString());
-            assertArrayEquals(bytes, f1.get());
+            byte[] jsonBytes = new byte[4096];
+            PlatformDependent.threadLocalRandom().nextBytes(jsonBytes);
+
+            f1.addContent(Unpooled.wrappedBuffer(jsonBytes, 0, 1024), false);
+            f1.addContent(Unpooled.wrappedBuffer(jsonBytes, 1024, jsonBytes.length - 1024), true);
+            assertArrayEquals(jsonBytes, f1.get());
+
             File file = f1.getFile();
-            assertEquals((long) bytes.length, file.length());
+            assertEquals(jsonBytes.length, file.length());
+
             FileInputStream fis = new FileInputStream(file);
             try {
-                byte[] buf = new byte[bytes.length];
+                byte[] buf = new byte[jsonBytes.length];
                 int offset = 0;
                 int read = 0;
                 int len = buf.length;
@@ -133,7 +136,7 @@ public class DiskFileUploadTest {
                         break;
                     }
                 }
-                assertArrayEquals(bytes, buf);
+                assertArrayEquals(jsonBytes, buf);
             } finally {
                 fis.close();
             }