Gillian Anderson's estranged husband Julian Ozanne is set to demand a paternity test when the actress' baby is born.The 'X Files' star split from photojournalist and filmmaker Ozanne in April, after being married for less than two years.Just three months later Anderson - who already has an 11-year-old daughter, Piper, from her first marriage to Canadian television art director Clyde Klotz, which ended in 1996 - announced she was expecting a baby with wheel-clamping firm director Mark Griffiths.Ozanne is not convinced the baby is definitely Griffiths' and is set to ask for a paternity test as soon as the tot enters the world in just a few weeks time.A source told Britain's Mail On Sunday newspaper: "The split has been very hard for them both, but Julian has not ruled out the possibility he might be the father. Gillian and Julian split in April and she announced her pregnancy when she was three months gone, so the timing is pretty close. "Julian wants to be sure. He has spoken to several people about this and they have all told him to get a paternity test carried out - which he is seriously thinking about."