Yeah, where are you putting the code?
Edit: I do this in one of my plugins:
PHP Code:
elay)
{
SetEntPropEnt(entity, Prop_Data, "m_hPhysicsAttacker", client);
SetEntPropFloat(entity, Prop_Data, "m_flLastPhysicsInfluenceTime", GetGameTime());
I think that last line might be required, I see it in a few of mine like this.