Hartmann does it for Geylang again
It was a fairly even game between both sides and chances were few and far between, with the first real chance of the game coming in the 19th minute.
Shawal Anuar laid the ball on for Carlos Delgado and he drilled just wide from distance before Stanely Ng flicked a header past the post ten minutes later.
Ng turned provider in the36th minute but Shawal's header had a tad too much height as it went over the bar.
Geylang were given a fright just before the break when Hafiz Rahim sent a free-kick towards goal and what seemed like a routine save was fumbled out for a corner by Hairul Syirhan.
The Warriors suffered a heart attack of their own after the break, as Basil Chan had to parry away a innocuous free-kick by Hartmann in the 49th minute.
The deadlock was nearly broken on the hour mark, when Kento Fukuda met Hafiz Rahim's corner but his shot was hacked off the line.
Geylang came close on several occasions thereafter but Ng was denied twice by Hairul as the Warriors held firm.
Let's hope we can get something, after all something is better than nothing
The winning goal finally came in the dying embers of the game, as Hartmann was fouled by Fukuda 20 yards away from goal.
Stepping up to take the set piece, Hartmann struck a beautiful effort over the wall into the bottom corner for his fourth goal in five games.
Geylang coach Hasrin Jailani was impressed by Hartmann yet again but he believed the whole team deserves praise for working their socks off.
The former Singapore international urged his side to maintain their form, as they hope to earn some consolation.
"What's left for us, we go and try to win it. At least we are in the Plate final, so let's see how it goes on Saturday," he added.
"Let's hope we can get something, after all something is better than nothing."
Warriors coach Razif Onn was disappointed by the defeat however, as he believed Geylang scarcely deserved their free-kick.
"I am very disappointed, we had an even game. Neither of us threatened each other. It was a half foul to me, The boys don't deserve to lose like that," he said.