diff --git a/src/Umbraco.Web.UI.NetCore/Startup.cs b/src/Umbraco.Web.UI.NetCore/Startup.cs
index deba559ed1..21faae22f2 100644
--- a/src/Umbraco.Web.UI.NetCore/Startup.cs
+++ b/src/Umbraco.Web.UI.NetCore/Startup.cs
@@ -63,6 +63,10 @@ namespace Umbraco.Web.UI.NetCore
                 options.AllowSynchronousIO = true;
             });
 
+            services.Configure<IISServerOptions>(options =>
+            {
+                options.AllowSynchronousIO = true;
+            });
         }
 
         // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.