Dundee's relegation from the Scottish Premiership confirmed
Hendry drilled in a Glenn Middleton cutback for his eighth goal since returning from a loan spell with Kilmarnock in January to ensure the Saints will face Arbroath or Inverness in the play-off.
The win moves them an unassailable six points clear of Mark McGhee's Dundee with only one game remaining, while Aberdeen stay 10th following a disappointing run of just two wins in 11 games since Jim Goodwin took over in February.
Dundee had given themselves a stay of execution on Tuesday evening with an emphatic 3-1 win over Hibs – the first victory since McGhee replaced James McPake as manager – but it came too little too late to save the Dens Park side, who’ll be competing in the cinch Championship next term.