diff --git a/Octokit.Reactive/Clients/ObservableRepositoryCommitsClients.cs b/Octokit.Reactive/Clients/ObservableRepositoryCommitsClients.cs
index 1689fe35..977a07f5 100644
--- a/Octokit.Reactive/Clients/ObservableRepositoryCommitsClients.cs
+++ b/Octokit.Reactive/Clients/ObservableRepositoryCommitsClients.cs
@@ -33,6 +33,11 @@ namespace Octokit.Reactive
         /// <returns>A <see cref="IObservable{CompareResult}"/> of <see cref="CompareResult"/> for the specified references.</returns>
         public IObservable<CompareResult> Compare(string owner, string name, string @base, string head)
         {
+            Ensure.ArgumentNotNullOrEmptyString(owner, "owner");
+            Ensure.ArgumentNotNullOrEmptyString(name, "name");
+            Ensure.ArgumentNotNullOrEmptyString(@base, "base");
+            Ensure.ArgumentNotNullOrEmptyString(head, "head");
+
             return _commit.Compare(owner, name, @base, head).ToObservable();
         }
 
@@ -45,6 +50,9 @@ namespace Octokit.Reactive
         /// <returns>A <see cref="IObservable{CompareResult}"/> of <see cref="CompareResult"/> for the specified references.</returns>
         public IObservable<CompareResult> Compare(int repositoryId, string @base, string head)
         {
+            Ensure.ArgumentNotNullOrEmptyString(@base, "base");
+            Ensure.ArgumentNotNullOrEmptyString(head, "head");
+
             return _commit.Compare(repositoryId, @base, head).ToObservable();
         }
 
diff --git a/Octokit.Tests/Clients/RespositoryCommitsClientTests.cs b/Octokit.Tests/Clients/RespositoryCommitsClientTests.cs
index 6bd02632..f27ba20d 100644
--- a/Octokit.Tests/Clients/RespositoryCommitsClientTests.cs
+++ b/Octokit.Tests/Clients/RespositoryCommitsClientTests.cs
@@ -14,7 +14,7 @@ namespace Octokit.Tests.Clients
             public void EnsuresNonNullArguments()
             {
                 Assert.Throws<ArgumentNullException>(
-                () => new RepositoryCommitsClient(null));
+                    () => new RepositoryCommitsClient(null));
             }
         }
 
diff --git a/Octokit.Tests/Octokit.Tests.csproj b/Octokit.Tests/Octokit.Tests.csproj
index dea83aef..ba16b864 100644
--- a/Octokit.Tests/Octokit.Tests.csproj
+++ b/Octokit.Tests/Octokit.Tests.csproj
@@ -247,6 +247,7 @@
     <Compile Include="Reactive\ObservableRepositoryDeployKeysClientTests.cs" />
     <Compile Include="Reactive\ObservableGistsTests.cs" />
     <Compile Include="Reactive\ObservableRepositoryHooksClientTests.cs" />
+    <Compile Include="Reactive\ObservableRespositoryCommitsClientTests.cs" />
     <Compile Include="Reactive\ObservableStarredClientTests.cs" />
     <Compile Include="Reactive\ObservableStatisticsClientTests.cs" />
     <Compile Include="Reactive\ObservableTeamsClientTests.cs" />
diff --git a/Octokit.Tests/Reactive/ObservableRespositoryCommitsClientTests.cs b/Octokit.Tests/Reactive/ObservableRespositoryCommitsClientTests.cs
new file mode 100644
index 00000000..21ad5b41
--- /dev/null
+++ b/Octokit.Tests/Reactive/ObservableRespositoryCommitsClientTests.cs
@@ -0,0 +1,347 @@
+using System;
+using NSubstitute;
+using Octokit.Reactive;
+using Xunit;
+
+namespace Octokit.Tests.Reactive
+{
+    public class RespositoryCommitsClientTests
+    {
+        public class TheCtor
+        {
+            [Fact]
+            public void EnsuresNonNullArguments()
+            {
+                Assert.Throws<ArgumentNullException>(
+                    () => new ObservableRepositoryCommitsClient(null));
+            }
+        }
+
+        public class TheCompareMethod
+        {
+            [Fact]
+            public void RequestsCorrectUrl()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                client.Compare("fake", "repo", "base", "head");
+
+                gitHubClient.Received().Repository.Commit.Compare("fake", "repo", "base", "head");
+            }
+
+            [Fact]
+            public void RequestsCorrectUrlByRepositoryId()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                client.Compare(1, "base", "head");
+
+                gitHubClient.Received().Repository.Commit.Compare(1, "base", "head");
+            }
+
+            [Fact]
+            public void EnsuresNonNullArguments()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                Assert.Throws<ArgumentNullException>(() => client.Compare(null, "name", "base", "head"));
+                Assert.Throws<ArgumentNullException>(() => client.Compare("owner", null, "base", "head"));
+                Assert.Throws<ArgumentNullException>(() => client.Compare("owner", "name", null, "head"));
+                Assert.Throws<ArgumentNullException>(() => client.Compare("owner", "name", "base", null));
+
+                Assert.Throws<ArgumentNullException>(() => client.Compare(1, null, "head"));
+                Assert.Throws<ArgumentNullException>(() => client.Compare(1, "base", null));
+
+                Assert.Throws<ArgumentException>(() => client.Compare("", "name", "base", "head"));
+                Assert.Throws<ArgumentException>(() => client.Compare("owner", "", "base", "head"));
+                Assert.Throws<ArgumentException>(() => client.Compare("owner", "name", "", "head"));
+                Assert.Throws<ArgumentException>(() => client.Compare("owner", "name", "base", ""));
+                Assert.Throws<ArgumentException>(() => client.Compare(1, "", "head"));
+                Assert.Throws<ArgumentException>(() => client.Compare(1, "base", ""));
+            }
+        }
+
+        public class TheGetMethod
+        {
+            [Fact]
+            public void RequestsCorrectUrl()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                client.Get("fake", "repo", "reference");
+
+                gitHubClient.Received().Repository.Commit.Get("fake", "repo", "reference");
+            }
+
+            [Fact]
+            public void RequestsCorrectUrlByRepositoryId()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                client.Get(1, "reference");
+
+                gitHubClient.Received().Repository.Commit.Get(1, "reference");
+            }
+
+            [Fact]
+            public void EnsuresNonNullArguments()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                Assert.Throws<ArgumentNullException>(() => client.Get(null, "name", "reference"));
+                Assert.Throws<ArgumentNullException>(() => client.Get("owner", null, "reference"));
+                Assert.Throws<ArgumentNullException>(() => client.Get("owner", "name", null));
+
+                Assert.Throws<ArgumentNullException>(() => client.Get(1, null));
+
+                Assert.Throws<ArgumentException>(() => client.Get("", "name", "reference"));
+                Assert.Throws<ArgumentException>(() => client.Get("owner", "", "reference"));
+                Assert.Throws<ArgumentException>(() => client.Get("owner", "name", ""));
+
+                Assert.Throws<ArgumentException>(() => client.Get(1, ""));
+            }
+        }
+
+        public class TheGetAllMethod
+        {
+            [Fact]
+            public void RequestsCorrectUrl()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                client.GetAll("fake", "repo");
+
+                gitHubClient.Received().Repository.Commit.GetAll("fake", "repo");
+            }
+
+            [Fact]
+            public void RequestsCorrectUrlByRepositoryId()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                client.GetAll(1);
+
+                gitHubClient.Received().Repository.Commit.GetAll(1);
+            }
+
+            [Fact]
+            public void RequestsCorrectUrlWithApiOptions()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                var options = new ApiOptions
+                {
+                    PageCount = 1,
+                    StartPage = 1,
+                    PageSize = 1
+                };
+
+                client.GetAll("fake", "repo", options);
+
+                gitHubClient.Received().Repository.Commit.GetAll("fake", "repo", options);
+            }
+
+            [Fact]
+            public void RequestsCorrectUrlByRepositoryIdWithApiOptions()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                var options = new ApiOptions
+                {
+                    PageCount = 1,
+                    StartPage = 1,
+                    PageSize = 1
+                };
+
+                client.GetAll(1, options);
+
+                gitHubClient.Received().Repository.Commit.GetAll(1, options);
+            }
+
+            [Fact]
+            public void RequestsCorrectUrlParameterized()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                var commitRequest = new CommitRequest
+                {
+                    Author = "author",
+                    Sha = "sha",
+                    Path = "path",
+                    Since = null,
+                    Until = null
+                };
+
+                client.GetAll("fake", "repo", commitRequest);
+
+                gitHubClient.Received().Repository.Commit.GetAll("fake", "repo", commitRequest);
+            }
+
+            [Fact]
+            public void RequestsCorrectUrlByRepositoryIdParameterized()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                var commitRequest = new CommitRequest
+                {
+                    Author = "author",
+                    Sha = "sha",
+                    Path = "path",
+                    Since = null,
+                    Until = null
+                };
+
+                client.GetAll(1, commitRequest);
+
+                gitHubClient.Received().Repository.Commit.GetAll(1, commitRequest);
+            }
+
+            [Fact]
+            public void RequestsCorrectUrlWithApiOptionsParameterized()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                var commitRequest = new CommitRequest
+                {
+                    Author = "author",
+                    Sha = "sha",
+                    Path = "path",
+                    Since = null,
+                    Until = null
+                };
+
+                var options = new ApiOptions
+                {
+                    PageCount = 1,
+                    StartPage = 1,
+                    PageSize = 1
+                };
+
+                client.GetAll("fake", "repo", commitRequest, options);
+
+                gitHubClient.Received().Repository.Commit.GetAll("fake", "repo", commitRequest, options);
+            }
+
+            [Fact]
+            public void RequestsCorrectUrlByRepositoryIdWithApiOptionsParameterized()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                var commitRequest = new CommitRequest
+                {
+                    Author = "author",
+                    Sha = "sha",
+                    Path = "path",
+                    Since = null,
+                    Until = null
+                };
+
+                var options = new ApiOptions
+                {
+                    PageCount = 1,
+                    StartPage = 1,
+                    PageSize = 1
+                };
+
+                client.GetAll(1, commitRequest, options);
+
+                gitHubClient.Received().Repository.Commit.GetAll(1, commitRequest, options);
+            }
+
+            [Fact]
+            public void EnsuresNonNullArguments()
+            {
+                var connection = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(connection);
+
+                Assert.Throws<ArgumentNullException>(() => client.GetAll(null, "name"));
+                Assert.Throws<ArgumentNullException>(() => client.GetAll("owner", null));
+
+                Assert.Throws<ArgumentNullException>(() => client.GetAll(null, "name", ApiOptions.None));
+                Assert.Throws<ArgumentNullException>(() => client.GetAll("owner", null, ApiOptions.None));
+                Assert.Throws<ArgumentNullException>(() => client.GetAll("owner", "name", (ApiOptions)null));
+
+                Assert.Throws<ArgumentNullException>(() => client.GetAll(null, "name", new CommitRequest()));
+                Assert.Throws<ArgumentNullException>(() => client.GetAll("owner", null, new CommitRequest()));
+                Assert.Throws<ArgumentNullException>(() => client.GetAll("owner", "name", (CommitRequest)null));
+
+                Assert.Throws<ArgumentNullException>(() => client.GetAll(null, "name", new CommitRequest(), ApiOptions.None));
+                Assert.Throws<ArgumentNullException>(() => client.GetAll("owner", null, new CommitRequest(), ApiOptions.None));
+                Assert.Throws<ArgumentNullException>(() => client.GetAll("owner", "name", null, ApiOptions.None));
+                Assert.Throws<ArgumentNullException>(() => client.GetAll("owner", "name", new CommitRequest(), null));
+
+                Assert.Throws<ArgumentNullException>(() => client.GetAll(1, (ApiOptions)null));
+                Assert.Throws<ArgumentNullException>(() => client.GetAll(1, (CommitRequest)null));
+                Assert.Throws<ArgumentNullException>(() => client.GetAll(1, null, ApiOptions.None));
+                Assert.Throws<ArgumentNullException>(() => client.GetAll(1, new CommitRequest(), null));
+
+                Assert.Throws<ArgumentException>(() => client.GetAll("", "name"));
+                Assert.Throws<ArgumentException>(() => client.GetAll("owner", ""));
+                Assert.Throws<ArgumentException>(() => client.GetAll("", "name", ApiOptions.None));
+                Assert.Throws<ArgumentException>(() => client.GetAll("owner", "", ApiOptions.None));
+                Assert.Throws<ArgumentException>(() => client.GetAll("", "name", new CommitRequest()));
+                Assert.Throws<ArgumentException>(() => client.GetAll("owner", "", new CommitRequest()));
+                Assert.Throws<ArgumentException>(() => client.GetAll("", "name", new CommitRequest(), ApiOptions.None));
+                Assert.Throws<ArgumentException>(() => client.GetAll("owner", "", new CommitRequest(), ApiOptions.None));
+            }
+        }
+
+        public class TheGetSha1Method
+        {
+            [Fact]
+            public void RequestsCorrectUrl()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                client.GetSha1("fake", "repo", "ref");
+
+                gitHubClient.Received().Repository.Commit.GetSha1("fake", "repo", "ref");
+            }
+
+            [Fact]
+            public void RequestsCorrectUrlByRepositoryId()
+            {
+                var gitHubClient = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(gitHubClient);
+
+                client.GetSha1(1, "ref");
+
+                gitHubClient.Received().Repository.Commit.GetSha1(1, "ref");
+            }
+
+            [Fact]
+            public void EnsuresNonNullArguments()
+            {
+                var connection = Substitute.For<IGitHubClient>();
+                var client = new ObservableRepositoryCommitsClient(connection);
+
+                Assert.Throws<ArgumentNullException>(() => client.GetSha1(null, "name", "ref"));
+                Assert.Throws<ArgumentNullException>(() => client.GetSha1("owner", null, "ref"));
+                Assert.Throws<ArgumentNullException>(() => client.GetSha1("owner", "name", null));
+
+                Assert.Throws<ArgumentNullException>(() => client.GetSha1(1, null));
+
+                Assert.Throws<ArgumentException>(() => client.GetSha1("", "name", "ref"));
+                Assert.Throws<ArgumentException>(() => client.GetSha1("owner", "", "ref"));
+                Assert.Throws<ArgumentException>(() => client.GetSha1("owner", "name", ""));
+
+                Assert.Throws<ArgumentException>(() => client.GetSha1(1, ""));
+            }
+        }
+    }
+}
\ No newline at end of file