Disclosed in this specification is a method comprising inserting an anti-whitened data portion into a data packet that is to be whitened by whitening to yield a whitened data packet for transmission (44) from a first radio communications apparatus (30) to a second radio communications apparatus (10), the anti-whitened data portion having been determined based on anti-whitening data received (43) from the second radio communications apparatus (10) at the first radio communications apparatus, wherein the anti-whitened data portion is obtainable from a specific data block by anti-whitening, the anti-whitening compensating for the whitening so that the whitened data packet comprises the specific data block in non-whitened form.