Alexandre Lacazette came off the bench to score the winner, but the goal was only given after VAR over-ruled the original offside decision.
We had toiled all afternoon against a resolute Hammers side, but made the breakthrough when Mesut Ozil headed Pierre-Emerick Aubameyang's pass back across goal for Lacazette to smash home.
The flag was up against Ozil, but VAR replays showed he was just - just onside.
But for large parts of the game we didn't manage to test former Gunner Fabianksi in the West Ham goal at all, indeed it was the visitors who came closest in a fairly dour opening 45 minutes.