Roslaunch : include same .launch several times with different parameters

Hi all, I have a .launch file who include 6 times the same launch but with different parameters. But they all take the last "model" arg, does someone know why ? Example with only 2 includes : In spawn_car.launch, I'm using "model" arg like this : And cars are spawned with same car_description (here with miniCooper urdf.xacro file). Help anyone ? :)