diff --git a/CoinbasePro.Specs/JsonFixtures/Websocket/WebSocketTypeResponseFixture.cs b/CoinbasePro.Specs/JsonFixtures/Websocket/WebSocketTypeResponseFixture.cs
index 5900db57..8a648a13 100644
--- a/CoinbasePro.Specs/JsonFixtures/Websocket/WebSocketTypeResponseFixture.cs
+++ b/CoinbasePro.Specs/JsonFixtures/Websocket/WebSocketTypeResponseFixture.cs
@@ -100,20 +100,21 @@ public static string CreateLevel2Response()
 }";
         }
 
-        public static string CreateReceivedResponse()
+        public static string CreateReceivedResponse(string clientOid)
         {
-            return @"
-{
+            return $@"
+{{
     ""type"": ""received"",
     ""time"": ""2014-11-07T08:19:27.028459Z"",
     ""product_id"": ""BTC-USD"",
+    ""client_oid"": ""{clientOid}"",
     ""sequence"": 10,
     ""order_id"": ""d50ec984-77a8-460a-b958-66f114b0de9b"",
     ""size"": ""1.34"",
     ""price"": ""502.1"",
     ""side"": ""buy"",
     ""order_type"": ""limit""
-}";
+}}";
         }
 
         public static string CreateOpenResponse()
diff --git a/CoinbasePro.Specs/WebSocket/WebSocketSpecs.cs b/CoinbasePro.Specs/WebSocket/WebSocketSpecs.cs
index c6a25620..dba2bad1 100644
--- a/CoinbasePro.Specs/WebSocket/WebSocketSpecs.cs
+++ b/CoinbasePro.Specs/WebSocket/WebSocketSpecs.cs
@@ -257,16 +257,33 @@ class when_response_type_is_heartbeat
 
                 class when_response_type_is_received
                 {
-                    Because of = () =>
+                    class with_client_oid
                     {
-                        Subject.Start(product_type_inputs, no_channel_type_inputs);
+                        Because of = () =>
+                        {
+                            Subject.Start(product_type_inputs, no_channel_type_inputs);
 
-                        websocket_feed.Raise(e => e.MessageReceived += null, new MessageReceivedEventArgs(WebSocketTypeResponseFixture.CreateReceivedResponse()));
-                    };
+                            websocket_feed.Raise(e => e.MessageReceived += null, new MessageReceivedEventArgs(WebSocketTypeResponseFixture.CreateReceivedResponse("d0c5340b-6d6c-49d9-b567-48c4bfca13d2")));
+                        };
 
-                    It should_have_invoked_received_response = () =>
-                        The<IWebSocketFeed>().
-                            WasToldTo(p => p.Invoke(Param.IsAny<EventHandler<WebfeedEventArgs<Received>>>(), Param.IsAny<object>(), Param.IsAny<WebfeedEventArgs<Received>>()));
+                        It should_have_invoked_received_response = () =>
+                            The<IWebSocketFeed>().
+                                WasToldTo(p => p.Invoke(Param.IsAny<EventHandler<WebfeedEventArgs<Received>>>(), Param.IsAny<object>(), Param.IsAny<WebfeedEventArgs<Received>>()));
+                    }
+
+                    class with_blank_client_oid
+                    {
+                        Because of = () =>
+                        {
+                            Subject.Start(product_type_inputs, no_channel_type_inputs);
+
+                            websocket_feed.Raise(e => e.MessageReceived += null, new MessageReceivedEventArgs(WebSocketTypeResponseFixture.CreateReceivedResponse(string.Empty)));
+                        };
+
+                        It should_have_invoked_received_response = () =>
+                            The<IWebSocketFeed>().
+                                WasToldTo(p => p.Invoke(Param.IsAny<EventHandler<WebfeedEventArgs<Received>>>(), Param.IsAny<object>(), Param.IsAny<WebfeedEventArgs<Received>>()));
+                    }
                 }
 
                 class when_response_type_is_open
diff --git a/CoinbasePro/WebSocket/Models/Response/Received.cs b/CoinbasePro/WebSocket/Models/Response/Received.cs
index 8a2dac55..9f93fd0e 100644
--- a/CoinbasePro/WebSocket/Models/Response/Received.cs
+++ b/CoinbasePro/WebSocket/Models/Response/Received.cs
@@ -16,7 +16,7 @@ public class Received : BaseMessage
 
         public OrderSide Side { get; set; }
 
-        public Guid ClientOid { get; set; }
+        public Guid? ClientOid { get; set; }
 
         public ProductType ProductId { get; set; }