diff --git a/machine.capnp b/machine.capnp
index 2b31750..38254fe 100644
--- a/machine.capnp
+++ b/machine.capnp
@@ -38,6 +38,7 @@ struct Machine {
     manager @5:User;
     wiki @13 :Text;
     urn @14 :Text;
+    category @15 :Text;
 
     info @6 :Info;
     interface Info $CSharp.name("InfoInterface") {