Mario Gomez scored a 35th-minute penalty as Wolfsburg built a slender advantage in the first leg of their Bundesliga playoff with Eintracht Braunschweig.
Gomez slotted the spot-kick past visiting keeper Jasmin Fejzic, who had earlier pulled off good saves to deny Wolfsburg pair Yunus Malli and Daniel Didavi.
Braunschweig were unhappy with referee Sascha Stegemann's decision to award the penalty. Gomez had already handled the ball to try and control it, and there was little Valsvik could do to Yunus Malli's shot from the follow-up hitting his arm.
The visitors also looked dangerous in a tough local derby, and Mirko Boland should have done better with an early chance to put his side ahead.
Wolfsburg looked stronger in the early stages of the second half and Didavi steered a good chance into the side-netting.
Fejzic pulled off a fine stop to deny Gomez and also proved equal to a Malli free kick as the home side continued to press for a second.
But some resolute defending from Braunschweig gave them every chance of reversing the narrow deficit in their home second leg on Monday.
There was trouble before the game between Braunschweig fans and police. Police said they used a water cannon to control the situation after they were pelted with stones and bottles.