diff --git a/Octokit/Clients/RepositoriesClient.cs b/Octokit/Clients/RepositoriesClient.cs
index 5ea179b0..1808b3e4 100644
--- a/Octokit/Clients/RepositoriesClient.cs
+++ b/Octokit/Clients/RepositoriesClient.cs
@@ -81,7 +81,7 @@ namespace Octokit.Clients
             Ensure.ArgumentNotNull(data, "data");
 
             var endpoint = release.UploadUrl.ExpandUriTemplate(new { name = data.FileName });
-            return await Client.Upload<ReleaseAsset>(endpoint, data.RawData, new Dictionary<string, string> { { "Content-Type", data.ContentType } });
+            return await Client.Upload<ReleaseAsset>(endpoint, data.RawData, new Dictionary<string, string> { { "Content-Type", data.ContentType }, { "Accept", "application/vnd.github.manifold-preview" } });
         }
     }
 }