diff --git a/src/Microsoft.AspNet.Server.Kestrel/ServerFactory.cs b/src/Microsoft.AspNet.Server.Kestrel/ServerFactory.cs
index 9f7ad6789b..d1025b13b8 100644
--- a/src/Microsoft.AspNet.Server.Kestrel/ServerFactory.cs
+++ b/src/Microsoft.AspNet.Server.Kestrel/ServerFactory.cs
@@ -55,7 +55,14 @@ namespace Microsoft.AspNet.Server.Kestrel
 
                 disposables.Push(engine);
 
-                engine.Start(information.ThreadCount <= 0 ? 1 : information.ThreadCount);
+                if (information.ThreadCount < 0)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(information.ThreadCount), 
+                        information.ThreadCount, 
+                        "ThreadCount cannot be negative");
+                }
+
+                engine.Start(information.ThreadCount == 0 ? 1 : information.ThreadCount);
 
                 foreach (var address in information.Addresses)
                 {