Paris Saint-Germain lead Lens 1-0 at the Parc des Princes after David Luiz's free kick on the stroke of half time.
Luiz headed narrowly over the bar within the opening minute as the hosts began on the front foot, and they nearly made their early pressure pay when Ezequiel Lavezzi fed Jean-Christophe Bahebeck, but the young French striker could only prod narrowly wide.
Zlatan Ibrahimovic sent a free kick way over the top on 13 minutes and then smashed an effort onto the crossbar from close range just a minute later.
Ibrahimovic then fluffed his lines when he found himself with only Rudy Riou to beat, with his attempted chip far too easy for the Lens goalkeeper to claim.
Laurent Blanc's side felt that they should have had a penalty just after the half-hour mark, but their cries for handball fell on deaf ears.
Riou's timely interception then prevented Luiz from connecting with a Lavezzi cross as a resolute Lens side looked set to go in level at the break.
That was until Luiz stepped up to hammer home a free kick seconds before the break and leave Lens with a lot to do in the second half.
