diff --git a/src/Microsoft.AspNetCore.Sockets.Http/HttpConnectionDispatcher.cs b/src/Microsoft.AspNetCore.Sockets.Http/HttpConnectionDispatcher.cs
index e63944a7bd..e4c66205e0 100644
--- a/src/Microsoft.AspNetCore.Sockets.Http/HttpConnectionDispatcher.cs
+++ b/src/Microsoft.AspNetCore.Sockets.Http/HttpConnectionDispatcher.cs
@@ -170,7 +170,7 @@ namespace Microsoft.AspNetCore.Sockets
 
                         // The connection was disposed
                         context.Response.StatusCode = StatusCodes.Status404NotFound;
-                        context.Response.ContentType = "plain/text";
+                        context.Response.ContentType = "text/plain";
                         return;
                     }