README.md

README.md

@@ -110,8 +110,9 @@ buses.
 
 Currently supported:
 
-* Modbus (RTU/TCP) via [`io::modbus`]
-  ([Modbus PLC example](https://github.com/eva-ics/roboplc/blob/main/examples/plc-modbus.rs))
+* Modbus (RTU/TCP) via [`io::modbus`] ([Modbus PLC
+  example](https://github.com/eva-ics/roboplc/blob/main/examples/plc-modbus.rs)),
+  requires `modbus` crate feature.
 
 * Raw UDP in/out via [`io::raw_udp`]
   ([Raw UDP in/out example](https://github.com/eva-ics/roboplc/blob/main/examples/raw-udp.rs))