diff --git a/Octokit.Tests/Clients/AuthorizationsClientTests.cs b/Octokit.Tests/Clients/AuthorizationsClientTests.cs
index 955dbfdb..6e190a81 100644
--- a/Octokit.Tests/Clients/AuthorizationsClientTests.cs
+++ b/Octokit.Tests/Clients/AuthorizationsClientTests.cs
@@ -127,20 +127,18 @@ namespace Octokit.Tests.Clients
             }
 
             [Fact]
-            public void WrapsTwoFactorFailureWithTwoFactorException()
+            public async Task WrapsTwoFactorFailureWithTwoFactorException()
             {
                 var data = new NewAuthorization();
                 var client = Substitute.For<IApiConnection>();
                 client.Put<Authorization>(Args.Uri, Args.Object, Args.String)
-                    .Returns(_ =>
-                    {
-                        throw new AuthorizationException(
-                            new ApiResponse<object> { StatusCode = HttpStatusCode.Unauthorized});
-                    });
+                    .ThrowsAsync<Authorization>(
+                    new AuthorizationException(
+                        new ApiResponse<object> { StatusCode = HttpStatusCode.Unauthorized }));
                 var authEndpoint = new AuthorizationsClient(client);
 
-                Assert.Throws<TwoFactorChallengeFailedException>(() =>
-                    authEndpoint.GetOrCreateApplicationAuthentication("clientId", "secret", data, "authenticationCode"));
+                await AssertEx.Throws<TwoFactorChallengeFailedException>(async () =>
+                    await authEndpoint.GetOrCreateApplicationAuthentication("clientId", "secret", data, "authenticationCode"));
             }
 
             [Fact]
diff --git a/Octokit.Tests/Helpers/NSubstituteExtensions.cs b/Octokit.Tests/Helpers/NSubstituteExtensions.cs
new file mode 100644
index 00000000..97c1e053
--- /dev/null
+++ b/Octokit.Tests/Helpers/NSubstituteExtensions.cs
@@ -0,0 +1,19 @@
+using System;
+using System.Threading.Tasks;
+using NSubstitute;
+using NSubstitute.Core;
+
+public static class NSubstituteExtensions
+{
+    public static ConfiguredCall ReturnsAsync<TTask, TTaskType>(
+        this TTask value, Func<CallInfo, TTaskType> returnThis,
+        params Func<CallInfo, TTaskType>[] returnThese) where TTask : Task<TTaskType>
+    {
+        return value.Returns(callInfo => Task.Factory.StartNew(() => returnThis(callInfo)));
+    }
+
+    public static ConfiguredCall ThrowsAsync<T>(this Task<T> value, Exception exception)
+    {
+        return value.ReturnsAsync<Task<T>, T>(callInfo => { throw exception; });
+    }
+}
diff --git a/Octokit.Tests/OctoKit.Tests-NetCore45.csproj b/Octokit.Tests/OctoKit.Tests-NetCore45.csproj
index 1b4ba7b3..bfd3c35d 100644
--- a/Octokit.Tests/OctoKit.Tests-NetCore45.csproj
+++ b/Octokit.Tests/OctoKit.Tests-NetCore45.csproj
@@ -79,6 +79,7 @@
     <Compile Include="Exceptions\RateLimitExceededExceptionTests.cs" />
     <Compile Include="Exceptions\TwoFactorChallengeFailedException.cs" />
     <Compile Include="Exceptions\TwoFactorRequiredExceptionTests.cs" />
+    <Compile Include="Helpers\NSubstituteExtensions.cs" />
     <Compile Include="Helpers\UriExtensionsTests.cs" />
     <Compile Include="Http\ApiConnectionTests.cs" />
     <Compile Include="Clients\AuthorizationsClientTests.cs" />
diff --git a/Octokit.Tests/Octokit.Tests-Portable.csproj b/Octokit.Tests/Octokit.Tests-Portable.csproj
index 281a0d1e..d5eb3473 100644
--- a/Octokit.Tests/Octokit.Tests-Portable.csproj
+++ b/Octokit.Tests/Octokit.Tests-Portable.csproj
@@ -79,6 +79,7 @@
     <Compile Include="Exceptions\RateLimitExceededExceptionTests.cs" />
     <Compile Include="Exceptions\TwoFactorChallengeFailedException.cs" />
     <Compile Include="Exceptions\TwoFactorRequiredExceptionTests.cs" />
+    <Compile Include="Helpers\NSubstituteExtensions.cs" />
     <Compile Include="Helpers\UriExtensionsTests.cs" />
     <Compile Include="Http\ApiConnectionTests.cs" />
     <Compile Include="Clients\AuthorizationsClientTests.cs" />
diff --git a/Octokit.Tests/Octokit.Tests.csproj b/Octokit.Tests/Octokit.Tests.csproj
index 4a9dd735..64da5f2f 100644
--- a/Octokit.Tests/Octokit.Tests.csproj
+++ b/Octokit.Tests/Octokit.Tests.csproj
@@ -102,6 +102,7 @@
     <Compile Include="Exceptions\LoginAttemptsExceededExceptionTests.cs" />
     <Compile Include="Exceptions\RateLimitExceededExceptionTests.cs" />
     <Compile Include="Exceptions\TwoFactorRequiredExceptionTests.cs" />
+    <Compile Include="Helpers\NSubstituteExtensions.cs" />
     <Compile Include="Helpers\UriExtensionsTests.cs" />
     <Compile Include="Http\ApiConnectionTests.cs" />
     <Compile Include="Clients\AuthorizationsClientTests.cs" />
diff --git a/Octokit/Clients/AuthorizationsClient.cs b/Octokit/Clients/AuthorizationsClient.cs
index 29cb8957..df4a3014 100644
--- a/Octokit/Clients/AuthorizationsClient.cs
+++ b/Octokit/Clients/AuthorizationsClient.cs
@@ -117,7 +117,7 @@ namespace Octokit
         /// </exception>
         /// <exception cref="ApiException">Thrown when a general API error occurs.</exception>
         /// <returns>The created <see cref="Authorization"/>.</returns>
-        public Task<Authorization> GetOrCreateApplicationAuthentication(
+        public async Task<Authorization> GetOrCreateApplicationAuthentication(
             string clientId,
             string clientSecret,
             NewAuthorization newAuthorization,
@@ -139,7 +139,7 @@ namespace Octokit
 
             try
             {
-                return ApiConnection.Put<Authorization>(
+                return await ApiConnection.Put<Authorization>(
                     endpoint,
                     requestData,
                     twoFactorAuthenticationCode);