diff --git a/src/SlackConnector/Connections/Clients/Chat/FlurlChatClient.cs b/src/SlackConnector/Connections/Clients/Chat/FlurlChatClient.cs
index 9dfa7c7..f248c5f 100644
--- a/src/SlackConnector/Connections/Clients/Chat/FlurlChatClient.cs
+++ b/src/SlackConnector/Connections/Clients/Chat/FlurlChatClient.cs
@@ -21,21 +21,18 @@ public FlurlChatClient(IResponseVerifier responseVerifier)
 
         public async Task PostMessage(string slackKey, string channel, string text, IList<SlackAttachment> attachments)
         {
-            var request = ClientConstants
+            var response = await ClientConstants
                        .SlackApiHost
                        .AppendPathSegment(SEND_MESSAGE_PATH)
-                       .SetQueryParam("token", slackKey)
-                       .SetQueryParam("channel", channel)
-                       .SetQueryParam("text", text)
-                       .SetQueryParam("as_user", "true")
-                       .SetQueryParam("link_names", "true");
-            
-            if (attachments != null && attachments.Any())
-            {
-                request.SetQueryParam("attachments", JsonConvert.SerializeObject(attachments));
-            }
+                       .WithOAuthBearerToken(slackKey)
+                       .PostJsonAsync(new {
+                           channel = channel,
+                           text = text,
+                           as_user = true,
+                           link_names = true,
+                           attachments = attachments
+                       }).ReceiveJson<StandardResponse>();
 
-            var response = await request.GetJsonAsync<StandardResponse>();
             _responseVerifier.VerifyResponse(response);
         }
     }
diff --git a/tests/SlackConnector.Tests.Unit/Connections/Clients/Flurl/FlurlChatClientTests.cs b/tests/SlackConnector.Tests.Unit/Connections/Clients/Flurl/FlurlChatClientTests.cs
index 13f879d..5dc1288 100644
--- a/tests/SlackConnector.Tests.Unit/Connections/Clients/Flurl/FlurlChatClientTests.cs
+++ b/tests/SlackConnector.Tests.Unit/Connections/Clients/Flurl/FlurlChatClientTests.cs
@@ -50,18 +50,22 @@ public async Task should_call_expected_url_with_given_slack_key()
             _responseVerifierMock.Verify(x => x.VerifyResponse(Looks.Like(expectedResponse)));
             _httpTest
                 .ShouldHaveCalled(ClientConstants.SlackApiHost.AppendPathSegment(FlurlChatClient.SEND_MESSAGE_PATH))
-                .WithQueryParamValue("token", slackKey)
-                .WithQueryParamValue("channel", channel)
-                .WithQueryParamValue("text", text)
-                .WithQueryParamValue("as_user", "true")
-                .WithQueryParamValue("link_names", "true")
-                .WithoutQueryParam("attachments")
+                .WithOAuthBearerToken(slackKey)
+                .WithRequestJson(new
+                {
+                    channel = channel,
+                    text = text,
+                    as_user = true,
+                    link_names = true,
+                    attachments = (object)null
+                })
                 .Times(1);
         }
 
         [Fact]
         public async Task should_add_attachments_if_given()
         {
+            const string slackKey = "something-that-looks-like-a-slack-key";
             // given
             _httpTest.RespondWithJson(new StandardResponse());
             var attachments = new List<SlackAttachment>
@@ -71,12 +75,20 @@ public async Task should_add_attachments_if_given()
             };
 
             // when
-            await _chatClient.PostMessage(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>(), attachments);
+            await _chatClient.PostMessage(slackKey, It.IsAny<string>(), It.IsAny<string>(), attachments);
 
             // then
             _httpTest
                 .ShouldHaveCalled(ClientConstants.SlackApiHost.AppendPathSegment(FlurlChatClient.SEND_MESSAGE_PATH))
-                .WithQueryParamValue("attachments", JsonConvert.SerializeObject(attachments))
+                .WithOAuthBearerToken(slackKey)
+                .WithRequestJson(new
+                {
+                    channel = (string)null,
+                    text = (string)null,
+                    as_user = true,
+                    link_names = true,
+                    attachments = attachments
+                })
                 .Times(1);
         }
     }