A technique for transmitting and receiving a configuration message for a phase tracking reference signal, PT-RS, on a radio channel between a radio access node and a radio device is described. The radio channel comprises a plurality of subcarriers in a physical resource block, PRB. A subset of the subcarriers in the PRB is allocated to a demodulation reference signal, DM-RS. As to a method aspect of the technique, the configuration message is transmitted to the radio device. The configuration message comprises a bit field that is indicative of at least one subcarrier allocated to the PT-RS among the subset of subcarriers allocated to the DM-RS.