diff --git a/src/DohClient.cs b/src/DohClient.cs
index 1df6f69..d6e8d1c 100644
--- a/src/DohClient.cs
+++ b/src/DohClient.cs
@@ -121,9 +121,15 @@ public override async Task<Message> QueryAsync(
                 new CancellationTokenSource(Timeout).Token);
 
             // Post the request.
-            var content = new ByteArrayContent(request.ToByteArray());
-            content.Headers.ContentType = new MediaTypeHeaderValue(DnsWireFormat);
-            var httpResponse = await HttpClient.PostAsync(ServerUrl, content, cts.Token);
+            HttpResponseMessage httpResponse;
+            using (var ms = new MemoryStream())
+            {
+                request.Write(ms);
+                ms.Position = 0;
+                var content = new StreamContent(ms);
+                content.Headers.ContentType = new MediaTypeHeaderValue(DnsWireFormat);
+                httpResponse = await HttpClient.PostAsync(ServerUrl, content, cts.Token);
+            }
 
             // Check the HTTP response.
             httpResponse.EnsureSuccessStatusCode();
diff --git a/src/DotClient.cs b/src/DotClient.cs
index cdf804c..78d67c1 100644
--- a/src/DotClient.cs
+++ b/src/DotClient.cs
@@ -267,17 +267,17 @@ byte[] BuildRequest(Message request)
                     paddingOption.Padding = new byte[need];
             };
 
-            var udpRequest = request.ToByteArray();
-            byte[] length = BitConverter.GetBytes((ushort)udpRequest.Length);
-            if (BitConverter.IsLittleEndian)
+            using (var tcpRequest = new MemoryStream())
             {
-                Array.Reverse(length);
+                tcpRequest.WriteByte(0); // two byte length prefix
+                tcpRequest.WriteByte(0);
+                request.Write(tcpRequest); // udpRequest
+                var length = (ushort)(tcpRequest.Length - 2);
+                tcpRequest.Position = 0;
+                tcpRequest.WriteByte((byte) (length >> 8));
+                tcpRequest.WriteByte((byte) (length));
+                return tcpRequest.ToArray();
             }
-            var tcpRequest = new byte[length.Length + udpRequest.Length];
-            length.CopyTo(tcpRequest, 0);
-            udpRequest.CopyTo(tcpRequest, length.Length);
-
-            return tcpRequest;
         }
 
         /// <summary>