The biggest train drivers' union has suspended a strike ballot among its members on Southern Railway because of "technical difficulties."
Aslef had started asking its members if they wanted to take industrial action in a dispute over driver-only trains.
The result of the ballot was due within two weeks, raising the threat of strikes at the end of the month.
Aslef said it will reissue ballot papers to almost 1,000 drivers.
Southern still faces a series of strikes in the coming weeks by the Rail, Maritime and Transport union in the bitter dispute over the role of conductors.
The latest 48-hour walkout ended at midnight, with further stoppages planned later this month, early December, in the run up to Christmas and over new year.
The RMT is also balloting its driver members for strikes.
Angie Doll, Southern's passenger services director, said: "We're pleased that Aslef has called off this ballot. This welcome development gives us the time and opportunity to sit down with union officials to resolve their dispute."