Nilstorp was the backup to Richard Bachman before Tuesday's move. Bachman has made three straight starts since he had to replace starter Kari Lehtonen, who re-injured a groin early in a win over the Los Angeles Kings on April 9.
Bachman helped the Stars finish off a season-best five-game winning streak before Monday night's 5-2 loss to Chicago.
Nilstorp has bounced between Dallas and the Texas Stars most of the season. He's 1-3-1 with Dallas and 18-11-5 with Texas.
The Stars have two days off before playing Vancouver at home on Thursday night.
Unless he really collapses, I don't see him going anywhere. I've been very impressed with his composure and maturity. Once the regular season started, he was a different guy; it was like game on and almost as if he's been around for a long time.
— Florida Panthers general manager Dale Tallon on rookie defenseman Aaron Ekblad