diff --git a/server/modbus/readonlymode.go b/server/modbus/readonlymode.go
index 4be0eee1d..a954d3775 100644
--- a/server/modbus/readonlymode.go
+++ b/server/modbus/readonlymode.go
@@ -6,6 +6,6 @@ type ReadOnlyMode int
 
 const (
 	ReadOnlyFalse ReadOnlyMode = iota
-	ReadOnlyDeny
-	ReadOnlyTrue
+	ReadOnlyDeny               // return modbus error
+	ReadOnlyTrue               // silently ignore writes
 )