Promotion-chasing Sheffield United struggled to outmatch relegation-threatened Chesterfield in an ill-tempered first half at Bramall Lane.
United looked dangerous from the off, with Ched Evans and Michael Doyle missing the target with long-range shots inside the first 10 minutes.
Chesterfield came closest in the opening stages when Craig Westcarr's shot drifted wide of the United goal.
Both sides gave away multiple free kicks in what proved to be a scrappy opening twenty minutes, though neither capitalised from the other's indiscipline.
Matthew Lowton had a chance to break the deadlock for United at 36 minutes, forcing a save from Tommy Lee. Stephen Quinn blasted his follow-up over the bar.
At the other end, Chesterfield piled on the pressure at the half-hour mark. A shot by Westcarr struck Lowton on its way behind, and Josh Thompson tested keeper Steve Simonsen from the resulting corner.
United took the lead on 38 minutes when Lee Williamson drove the ball home from Evan's pass, but their advantage didn't last long.
Chesterfield responded six minutes later when Moussa powered an equaliser into the top corner from outside the area, leaving the score a 1-1 at the half-time whistle.
