Rail passengers face further disruption after senior conductors announced a fourth day of strike action in a pay dispute with bosses.
Members of the National Union of Rail, Maritime and Transport Workers who work for East Midland Trains are due to stage the third of three 24-hour walk-outs on Saturday.
The union has now announced it will also strike on August 17.
East Midlands Trains has run a revised timetable during the strikes but its London services are not affected.
Union bosses has raised concern about Sunday working and wage variation.
Stagecoach-owned East Midlands Trains, which will hand over the regional franchise to Abellio on August 18, said the contracts had been agreed with the union six years ago.