diff --git a/buffer/src/main/java/io/netty/buffer/ByteBufUtil.java b/buffer/src/main/java/io/netty/buffer/ByteBufUtil.java
index c56f322b7f..cd32a0fc90 100644
--- a/buffer/src/main/java/io/netty/buffer/ByteBufUtil.java
+++ b/buffer/src/main/java/io/netty/buffer/ByteBufUtil.java
@@ -17,6 +17,7 @@ package io.netty.buffer;
 
 import static io.netty.util.internal.ObjectUtil.checkNotNull;
 
+import io.netty.util.AsciiString;
 import io.netty.util.ByteProcessor;
 import io.netty.util.ByteString;
 import io.netty.util.CharsetUtil;
@@ -498,7 +499,10 @@ public final class ByteBufUtil {
         // ASCII uses 1 byte per char
         final int len = seq.length();
         buf.ensureWritable(len);
-        if (buf instanceof AbstractByteBuf) {
+        if (seq instanceof AsciiString) {
+            AsciiString asciiString = (AsciiString) seq;
+            buf.writeBytes(asciiString.array(), asciiString.arrayOffset(), asciiString.length());
+        } else if (buf instanceof AbstractByteBuf) {
             // Fast-Path
             AbstractByteBuf buffer = (AbstractByteBuf) buf;
             int writerIndex = buffer.writerIndex;
diff --git a/buffer/src/test/java/io/netty/buffer/ByteBufUtilTest.java b/buffer/src/test/java/io/netty/buffer/ByteBufUtilTest.java
index fcdf987317..9507d815b4 100644
--- a/buffer/src/test/java/io/netty/buffer/ByteBufUtilTest.java
+++ b/buffer/src/test/java/io/netty/buffer/ByteBufUtilTest.java
@@ -17,6 +17,8 @@ package io.netty.buffer;
 
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+
+import io.netty.util.AsciiString;
 import io.netty.util.CharsetUtil;
 import io.netty.util.ReferenceCountUtil;
 
@@ -105,4 +107,15 @@ public class ByteBufUtilTest {
 
         Assert.assertEquals(buf, buf2);
     }
+
+    @Test
+    public void testWriteUsAsciiString() {
+        AsciiString usAscii = new AsciiString("NettyRocks");
+        ByteBuf buf = ReferenceCountUtil.releaseLater(Unpooled.buffer(16));
+        buf.writeBytes(usAscii.toString().getBytes(CharsetUtil.US_ASCII));
+        ByteBuf buf2 = ReferenceCountUtil.releaseLater(Unpooled.buffer(16));
+        ByteBufUtil.writeAscii(buf2, usAscii);
+
+        Assert.assertEquals(buf, buf2);
+    }
 }