diff --git a/lnd.go b/lnd.go
index b4fde604..d5bc7768 100644
--- a/lnd.go
+++ b/lnd.go
@@ -145,6 +145,12 @@ type RPCSubserverConfig struct {
 	// per URI, they are all required. See rpcserver.go for a list of valid
 	// action and entity values.
 	Permissions map[string][]bakery.Op
+
+	// MacaroonValidator is a custom macaroon validator that should be used
+	// instead of the default lnd validator. If specified, the custom
+	// validator is used for all URIs specified in the above Permissions
+	// map.
+	MacaroonValidator macaroons.MacaroonValidator
 }
 
 // ListenerWithSignal is a net.Listener that has an additional Ready channel that
diff --git a/rpcserver.go b/rpcserver.go
index be6e7a8e..784179f4 100644
--- a/rpcserver.go
+++ b/rpcserver.go
@@ -661,10 +661,12 @@ func newRPCServer(cfg *Config, s *server, macService *macaroons.Service,
 		return nil, err
 	}
 
-	// External subserver possibly need to register their own permissions.
+	// External subserver possibly need to register their own permissions
+	// and macaroon validator.
 	for _, lis := range listeners {
 		extSubserver := lis.ExternalRPCSubserverCfg
 		if extSubserver != nil {
+			macValidator := extSubserver.MacaroonValidator
 			for method, ops := range extSubserver.Permissions {
 				// For each new method:ops combo, we also ensure
 				// that non of the sub-servers try to override
@@ -677,6 +679,23 @@ func newRPCServer(cfg *Config, s *server, macService *macaroons.Service,
 				}
 
 				permissions[method] = ops
+
+				// Give the external subservers the possibility
+				// to also use their own validator to check any
+				// macaroons attached to calls to this method.
+				// This allows them to have their own root key
+				// ID database and permission entities.
+				if macValidator != nil {
+					err := macService.RegisterExternalValidator(
+						method, macValidator,
+					)
+					if err != nil {
+						return nil, fmt.Errorf("could "+
+							"not register "+
+							"external macaroon "+
+							"validator: %v", err)
+					}
+				}
 			}
 		}
 	}