What is wrong with my prop_physics_override?

I want to spawn a model that has no physics object, but want to simulate some physics, so the spawned one can be moved around by the player. I don’t care if it looks good, the purpose is only to kick the prop around.
This is the code I used, and I’m pretty sure it worked a while ago, but now the spawned prop is not moving and stuck at the spawned position like it has no physics:

    local ent = ents.Create ("prop_physics_override")
    ent:SetModel ( "models/combine_camera/combine_camera.mdl" )
    ent:SetPos( Vector(0,0,0) ) --I use some random vectors here
    ent:SetAngles( Angle(0,0,0) ) --I use some random angles here
    ent:SetCollisionGroup( COLLISION_GROUP_DEBRIS )

I get this error in console on the call to the ent:Spawn():
ERROR!: Can’t create physics object for models/combine_camera/combine_camera.mdl

I’m aware that this model has no physics object (you can see it if you call ent:GetPhysicsObject() afterwards) but the purpose of prop_physics_override is to use your own physics on the model, isn’t it? So why this errormessage?
I use ents.Create with prop_physics_override because I use random models, some with and some without physics objects.

Is this a bug or I’m doing something wrong?

try another prop/model and tell me if it will work.

Use one of Entity:PhysicsInit*() functions to do this.

[editline]15th May 2013[/editline]