diff --git a/Octokit.Tests/Reactive/ObservableStarredClientTests.cs b/Octokit.Tests/Reactive/ObservableStarredClientTests.cs
index 8e6f38c0..6c3afbdb 100644
--- a/Octokit.Tests/Reactive/ObservableStarredClientTests.cs
+++ b/Octokit.Tests/Reactive/ObservableStarredClientTests.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Reactive.Linq;
+using System.Reactive.Threading.Tasks;
 using System.Threading.Tasks;
 using NSubstitute;
 using Octokit;
@@ -22,8 +23,8 @@ namespace Octokit.Tests.Reactive
             {
                 var client = new ObservableStarredClient(Substitute.For<IGitHubClient>());
 
-                await AssertEx.Throws<ArgumentException>(async () => await client.GetAllStargazers(null, "name"));
-                await AssertEx.Throws<ArgumentException>(async () => await client.GetAllStargazers("owner", null));
+                await Assert.ThrowsAsync<ArgumentException>(() => client.GetAllStargazers(null, "name").ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.GetAllStargazers("owner", null).ToTask());
             }
 
             [Fact]
@@ -61,7 +62,7 @@ namespace Octokit.Tests.Reactive
             {
                 var client = new ObservableStarredClient(Substitute.For<IGitHubClient>());
 
-                await AssertEx.Throws<ArgumentException>(async () => await client.GetAllForUser(null));
+                await Assert.ThrowsAsync<ArgumentException>(() => client.GetAllForUser(null).ToTask());
             }
 
             [Fact]
@@ -84,8 +85,8 @@ namespace Octokit.Tests.Reactive
             {
                 var client = new ObservableStarredClient(Substitute.For<IGitHubClient>());
 
-                await AssertEx.Throws<ArgumentException>(async () => await client.CheckStarred(null, "james"));
-                await AssertEx.Throws<ArgumentException>(async () => await client.CheckStarred("james", null));
+                await Assert.ThrowsAsync<ArgumentException>(() => client.CheckStarred(null, "james").ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.CheckStarred("james", null).ToTask());
             }
 
             [Fact]
@@ -106,8 +107,8 @@ namespace Octokit.Tests.Reactive
             {
                 var client = new ObservableStarredClient(Substitute.For<IGitHubClient>());
 
-                await AssertEx.Throws<ArgumentException>(async () => await client.StarRepo(null, "james"));
-                await AssertEx.Throws<ArgumentException>(async () => await client.StarRepo("james", null));
+                await Assert.ThrowsAsync<ArgumentException>(() => client.StarRepo(null, "james").ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.StarRepo("james", null).ToTask());
             }
 
             [Fact]
@@ -128,8 +129,8 @@ namespace Octokit.Tests.Reactive
             {
                 var client = new ObservableStarredClient(Substitute.For<IGitHubClient>());
 
-                await AssertEx.Throws<ArgumentException>(async () => await client.RemoveStarFromRepo(null, "james"));
-                await AssertEx.Throws<ArgumentException>(async () => await client.RemoveStarFromRepo("james", null));
+                await Assert.ThrowsAsync<ArgumentException>(() => client.RemoveStarFromRepo(null, "james").ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.RemoveStarFromRepo("james", null).ToTask());
             }
 
             [Fact]
diff --git a/Octokit.Tests/Reactive/ObservableStatisticsClientTests.cs b/Octokit.Tests/Reactive/ObservableStatisticsClientTests.cs
index f01f416f..62091a78 100644
--- a/Octokit.Tests/Reactive/ObservableStatisticsClientTests.cs
+++ b/Octokit.Tests/Reactive/ObservableStatisticsClientTests.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Reactive.Linq;
+using System.Reactive.Threading.Tasks;
 using System.Threading.Tasks;
 using NSubstitute;
 using Octokit.Reactive;
@@ -27,14 +28,14 @@ namespace Octokit.Tests.Reactive
             public async Task ThrowsIfGivenNullRepositoryName()
             {   
                 var statisticsClient = new ObservableStatisticsClient(Substitute.For<IGitHubClient>());
-                await AssertEx.Throws<ArgumentNullException>(async () => await statisticsClient.GetContributors("owner", null));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => statisticsClient.GetContributors("owner", null).ToTask());
             }
 
             [Fact]
             public async Task ThrowsIfGivenNullOwnerName()
             {
                 var statisticsClient = new ObservableStatisticsClient(Substitute.For<IGitHubClient>());
-                await AssertEx.Throws<ArgumentNullException>(async () => await statisticsClient.GetContributors(null, "repositoryName"));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => statisticsClient.GetContributors(null, "repositoryName").ToTask());
             }
         }
     }
diff --git a/Octokit.Tests/Reactive/ObservableTreesClientTests.cs b/Octokit.Tests/Reactive/ObservableTreesClientTests.cs
index 206ebf6c..cef264fc 100644
--- a/Octokit.Tests/Reactive/ObservableTreesClientTests.cs
+++ b/Octokit.Tests/Reactive/ObservableTreesClientTests.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Reactive.Linq;
+using System.Reactive.Threading.Tasks;
 using System.Threading.Tasks;
 using NSubstitute;
 using Octokit.Reactive;
@@ -28,12 +29,12 @@ namespace Octokit.Tests
             {
                 var client = new ObservableTreesClient(Substitute.For<IGitHubClient>());
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Get(null, "name", "123456ABCD"));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Get("", "name", "123456ABCD"));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Get("owner", null, "123456ABCD"));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Get("owner", "", "123456ABCD"));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.Get("owner", "name", null));
-                await AssertEx.Throws<ArgumentException>(async () => await client.Get("owner", "name", ""));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Get(null, "name", "123456ABCD").ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Get("", "name", "123456ABCD").ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Get("owner", null, "123456ABCD").ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Get("owner", "", "123456ABCD").ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.Get("owner", "name", null).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.Get("owner", "name", "").ToTask());
             }
         }
         
@@ -55,12 +56,12 @@ namespace Octokit.Tests
             {
                 var client = new ObservableTreesClient(Substitute.For<IGitHubClient>());
 
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.GetRecursive(null, "name", "123456ABCD"));
-                await AssertEx.Throws<ArgumentException>(async () => await client.GetRecursive("", "name", "123456ABCD"));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.GetRecursive("owner", null, "123456ABCD"));
-                await AssertEx.Throws<ArgumentException>(async () => await client.GetRecursive("owner", "", "123456ABCD"));
-                await AssertEx.Throws<ArgumentNullException>(async () => await client.GetRecursive("owner", "name", null));
-                await AssertEx.Throws<ArgumentException>(async () => await client.GetRecursive("owner", "name", ""));
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetRecursive(null, "name", "123456ABCD").ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.GetRecursive("", "name", "123456ABCD").ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetRecursive("owner", null, "123456ABCD").ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.GetRecursive("owner", "", "123456ABCD").ToTask());
+                await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetRecursive("owner", "name", null).ToTask());
+                await Assert.ThrowsAsync<ArgumentException>(() => client.GetRecursive("owner", "name", "").ToTask());
             }
         }