diff --git a/Octokit.Reactive/Clients/ObservableReleasesClient.cs b/Octokit.Reactive/Clients/ObservableReleasesClient.cs
index a2e61749..5e8bc578 100644
--- a/Octokit.Reactive/Clients/ObservableReleasesClient.cs
+++ b/Octokit.Reactive/Clients/ObservableReleasesClient.cs
@@ -191,6 +191,8 @@ namespace Octokit.Reactive
         /// <returns>The created <see cref="Release"/>.</returns>
         public IObservable<Release> Create(int repositoryId, NewRelease data)
         {
+            Ensure.ArgumentNotNull(data, "data");
+
             return _client.Create(repositoryId, data).ToObservable();
         }
 
diff --git a/Octokit.Tests/Reactive/ObservableReleasesClientTests.cs b/Octokit.Tests/Reactive/ObservableReleasesClientTests.cs
index f156964a..7d85c5ae 100644
--- a/Octokit.Tests/Reactive/ObservableReleasesClientTests.cs
+++ b/Octokit.Tests/Reactive/ObservableReleasesClientTests.cs
@@ -203,7 +203,7 @@ namespace Octokit.Tests.Reactive
             }
 
             [Fact]
-            public void EnsuresArgumentsNotNull()
+            public void EnsuresNonNullArguments()
             {
                 var releasesClient = new ObservableReleasesClient(Substitute.For<IGitHubClient>());
                 var data = new NewRelease("fake-tag");