diff --git a/discovery/Service.go b/discovery/Service.go
index a92d0d9..5742013 100644
--- a/discovery/Service.go
+++ b/discovery/Service.go
@@ -6,6 +6,7 @@ import (
 )
 
 const (
+	UnknownServiceKey     = "UNKNOWN"
 	DefaultServiceVendor  = "UNKNOWN"
 	DefaultServiceVersion = "UNKNOWN"
 )