diff --git a/src/WireMock.Net/Client/IFluentMockServerAdmin.cs b/src/WireMock.Net/Client/IFluentMockServerAdmin.cs
index 38fdfbee0..4d1791f7c 100644
--- a/src/WireMock.Net/Client/IFluentMockServerAdmin.cs
+++ b/src/WireMock.Net/Client/IFluentMockServerAdmin.cs
@@ -55,6 +55,7 @@ public interface IFluentMockServerAdmin
         /// </summary>
         /// <param name="mapping">MappingModel</param>
         [Post("__admin/mappings")]
+        [Header("Content-Type", "application/json")]
         Task<string> PostMappingAsync([Body] MappingModel mapping);
 
         /// <summary>
@@ -137,6 +138,7 @@ public interface IFluentMockServerAdmin
         /// </summary>
         /// <param name="model">The RequestModel</param>
         [Post("__admin/requests/find")]
+        [Header("Content-Type", "application/json")]
         Task<IList<LogEntryModel>> FindRequestsAsync([Body] RequestModel model);
 
         /// <summary>
diff --git a/test/WireMock.Net.Tests/ClientTests.cs b/test/WireMock.Net.Tests/ClientTests.cs
new file mode 100644
index 000000000..f522d1226
--- /dev/null
+++ b/test/WireMock.Net.Tests/ClientTests.cs
@@ -0,0 +1,48 @@
+using System.Linq;
+using System.Threading.Tasks;
+using NFluent;
+using RestEase;
+using WireMock.Admin.Mappings;
+using WireMock.Client;
+using WireMock.Server;
+using Xunit;
+
+namespace WireMock.Net.Tests
+{
+    public class ClientTests
+    {
+        [Fact]
+        public async Task Client_IFluentMockServerAdmin_PostMappingAsync()
+        {
+            // Assign
+            var server = FluentMockServer.StartWithAdminInterface();
+            var api = RestClient.For<IFluentMockServerAdmin>(server.Urls[0]);
+
+            // Act
+            var model = new MappingModel
+            {
+                Request = new RequestModel
+                {
+                    Path = "/1"
+                },
+                Response = new ResponseModel
+                {
+                    Body = "txt",
+                    StatusCode = 200
+                },
+                Priority = 500,
+                Title = "test"
+            };
+            string result = await api.PostMappingAsync(model);
+
+            // Assert
+            Check.That(result).IsNotNull();
+
+            var mapping = server.Mappings.Single(m => m.Priority == 500);
+            Check.That(mapping).IsNotNull();
+            Check.That(mapping.Title).Equals("test");
+
+            server.Stop();
+        }
+    }
+}
\ No newline at end of file