We present an improved algorithm to calculate the one-tap equalizer per subchannel in a DMT receiver in the case of a guard interval of insufficient length. The new equalizer reduces the symbol error rate at no additional computational and hardware cost. It is designed for a scenario where standard modems have to be used that do not allow time-domain or per-tone equalization or where the extra cost of these modules is undesired since in the majority of setups the guard interval is of sufficient length.