diff --git a/Octokit.Reactive/Clients/ObservablePullRequestsClient.cs b/Octokit.Reactive/Clients/ObservablePullRequestsClient.cs
index e6b77d3fae..96a1bd3fa2 100644
--- a/Octokit.Reactive/Clients/ObservablePullRequestsClient.cs
+++ b/Octokit.Reactive/Clients/ObservablePullRequestsClient.cs
@@ -111,7 +111,7 @@ public IObservable<PullRequest> GetAllForRepository(string owner, string name, A
             Ensure.ArgumentNotNullOrEmptyString(name, nameof(name));
             Ensure.ArgumentNotNull(options, nameof(options));
 
-            return _connection.GetAndFlattenAllPages<PullRequest>(ApiUrls.PullRequests(owner, name), options);
+            return _connection.GetAndFlattenAllPages<PullRequest>(ApiUrls.PullRequests(owner, name), null, AcceptHeaders.DraftPullRequestApiPreview, options);
         }
 
         /// <summary>
@@ -126,7 +126,7 @@ public IObservable<PullRequest> GetAllForRepository(long repositoryId, ApiOption
         {
             Ensure.ArgumentNotNull(options, nameof(options));
 
-            return _connection.GetAndFlattenAllPages<PullRequest>(ApiUrls.PullRequests(repositoryId), options);
+            return _connection.GetAndFlattenAllPages<PullRequest>(ApiUrls.PullRequests(repositoryId), null, AcceptHeaders.DraftPullRequestApiPreview, options);
         }
 
         /// <summary>
@@ -180,7 +180,7 @@ public IObservable<PullRequest> GetAllForRepository(string owner, string name, P
             Ensure.ArgumentNotNull(options, nameof(options));
 
             return _connection.GetAndFlattenAllPages<PullRequest>(ApiUrls.PullRequests(owner, name),
-                request.ToParametersDictionary(), options);
+                request.ToParametersDictionary(), AcceptHeaders.DraftPullRequestApiPreview, options);
         }
 
         /// <summary>
@@ -198,7 +198,7 @@ public IObservable<PullRequest> GetAllForRepository(long repositoryId, PullReque
             Ensure.ArgumentNotNull(options, nameof(options));
 
             return _connection.GetAndFlattenAllPages<PullRequest>(ApiUrls.PullRequests(repositoryId),
-                request.ToParametersDictionary(), options);
+                request.ToParametersDictionary(), AcceptHeaders.DraftPullRequestApiPreview, options);
         }
 
         /// <summary>
diff --git a/Octokit.Tests/Reactive/ObservablePullRequestsClientTests.cs b/Octokit.Tests/Reactive/ObservablePullRequestsClientTests.cs
index b76e89bdf2..4109c2d1ff 100644
--- a/Octokit.Tests/Reactive/ObservablePullRequestsClientTests.cs
+++ b/Octokit.Tests/Reactive/ObservablePullRequestsClientTests.cs
@@ -209,11 +209,11 @@ public async Task ReturnsEveryPageOfPullRequests()
                     }
                 );
                 var gitHubClient = Substitute.For<IGitHubClient>();
-                gitHubClient.Connection.Get<List<PullRequest>>(firstPageUrl, Args.EmptyDictionary, null)
+                gitHubClient.Connection.Get<List<PullRequest>>(firstPageUrl, Args.EmptyDictionary, "application/vnd.github.shadow-cat-preview+json")
                     .Returns(Task.Factory.StartNew<IApiResponse<List<PullRequest>>>(() => firstPageResponse));
-                gitHubClient.Connection.Get<List<PullRequest>>(secondPageUrl, Args.EmptyDictionary, null)
+                gitHubClient.Connection.Get<List<PullRequest>>(secondPageUrl, Args.EmptyDictionary, "application/vnd.github.shadow-cat-preview+json")
                     .Returns(Task.Factory.StartNew<IApiResponse<List<PullRequest>>>(() => secondPageResponse));
-                gitHubClient.Connection.Get<List<PullRequest>>(thirdPageUrl, Args.EmptyDictionary, null)
+                gitHubClient.Connection.Get<List<PullRequest>>(thirdPageUrl, Args.EmptyDictionary, "application/vnd.github.shadow-cat-preview+json")
                     .Returns(Task.Factory.StartNew<IApiResponse<List<PullRequest>>>(() => lastPageResponse));
                 var client = new ObservablePullRequestsClient(gitHubClient);
 
@@ -262,11 +262,11 @@ public async Task ReturnsEveryPageOfPullRequestsWithRepositoryId()
                     }
                 );
                 var gitHubClient = Substitute.For<IGitHubClient>();
-                gitHubClient.Connection.Get<List<PullRequest>>(firstPageUrl, Args.EmptyDictionary, null)
+                gitHubClient.Connection.Get<List<PullRequest>>(firstPageUrl, Args.EmptyDictionary, "application/vnd.github.shadow-cat-preview+json")
                     .Returns(Task.Factory.StartNew<IApiResponse<List<PullRequest>>>(() => firstPageResponse));
-                gitHubClient.Connection.Get<List<PullRequest>>(secondPageUrl, Args.EmptyDictionary, null)
+                gitHubClient.Connection.Get<List<PullRequest>>(secondPageUrl, Args.EmptyDictionary, "application/vnd.github.shadow-cat-preview+json")
                     .Returns(Task.Factory.StartNew<IApiResponse<List<PullRequest>>>(() => secondPageResponse));
-                gitHubClient.Connection.Get<List<PullRequest>>(thirdPageUrl, Args.EmptyDictionary, null)
+                gitHubClient.Connection.Get<List<PullRequest>>(thirdPageUrl, Args.EmptyDictionary, "application/vnd.github.shadow-cat-preview+json")
                     .Returns(Task.Factory.StartNew<IApiResponse<List<PullRequest>>>(() => lastPageResponse));
                 var client = new ObservablePullRequestsClient(gitHubClient);
 
@@ -321,21 +321,21 @@ public async Task SendsAppropriateParametersMulti()
                         && d["state"] == "open"
                         && d["base"] == "fake_base_branch"
                         && d["sort"] == "created"
-                        && d["direction"] == "desc"), Arg.Any<string>())
+                        && d["direction"] == "desc"), "application/vnd.github.shadow-cat-preview+json")
                     .Returns(Task.Factory.StartNew<IApiResponse<List<PullRequest>>>(() => firstPageResponse));
                 gitHubClient.Connection.Get<List<PullRequest>>(secondPageUrl, Arg.Is<Dictionary<string, string>>(d => d.Count == 5
                         && d["head"] == "user:ref-name"
                         && d["state"] == "open"
                         && d["base"] == "fake_base_branch"
                         && d["sort"] == "created"
-                        && d["direction"] == "desc"), null)
+                        && d["direction"] == "desc"), "application/vnd.github.shadow-cat-preview+json")
                     .Returns(Task.Factory.StartNew<IApiResponse<List<PullRequest>>>(() => secondPageResponse));
                 gitHubClient.Connection.Get<List<PullRequest>>(thirdPageUrl, Arg.Is<Dictionary<string, string>>(d => d.Count == 5
                         && d["head"] == "user:ref-name"
                         && d["state"] == "open"
                         && d["base"] == "fake_base_branch"
                         && d["sort"] == "created"
-                        && d["direction"] == "desc"), null)
+                        && d["direction"] == "desc"), "application/vnd.github.shadow-cat-preview+json")
                     .Returns(Task.Factory.StartNew<IApiResponse<List<PullRequest>>>(() => lastPageResponse));
                 var client = new ObservablePullRequestsClient(gitHubClient);
 
@@ -390,21 +390,21 @@ public async Task SendsAppropriateParametersMultiWithRepositoryId()
                         && d["state"] == "open"
                         && d["base"] == "fake_base_branch"
                         && d["sort"] == "created"
-                        && d["direction"] == "desc"), Arg.Any<string>())
+                        && d["direction"] == "desc"), "application/vnd.github.shadow-cat-preview+json")
                     .Returns(Task.Factory.StartNew<IApiResponse<List<PullRequest>>>(() => firstPageResponse));
                 gitHubClient.Connection.Get<List<PullRequest>>(secondPageUrl, Arg.Is<Dictionary<string, string>>(d => d.Count == 5
                         && d["head"] == "user:ref-name"
                         && d["state"] == "open"
                         && d["base"] == "fake_base_branch"
                         && d["sort"] == "created"
-                        && d["direction"] == "desc"), null)
+                        && d["direction"] == "desc"), "application/vnd.github.shadow-cat-preview+json")
                     .Returns(Task.Factory.StartNew<IApiResponse<List<PullRequest>>>(() => secondPageResponse));
                 gitHubClient.Connection.Get<List<PullRequest>>(thirdPageUrl, Arg.Is<Dictionary<string, string>>(d => d.Count == 5
                         && d["head"] == "user:ref-name"
                         && d["state"] == "open"
                         && d["base"] == "fake_base_branch"
                         && d["sort"] == "created"
-                        && d["direction"] == "desc"), null)
+                        && d["direction"] == "desc"), "application/vnd.github.shadow-cat-preview+json")
                     .Returns(Task.Factory.StartNew<IApiResponse<List<PullRequest>>>(() => lastPageResponse));
                 var client = new ObservablePullRequestsClient(gitHubClient);