Help with xacro default values

Hello everybody, I have seen an interesting tool that I wanted to use : default values for parameters in xacro http://wiki.ros.org/xacro#Default_parameters But when I am trying to use it, the model can't be loaded. There is some test that I made : `` invalid parameter min_angle `` invalid parameter min_angle `` Invalid parameter "roll" This model works perfectly when I don't try to use default values. I am using ROS indigo 1.11.20. There is my questions : Do i need to set a default value for each parameter ? Is there an obvious mistake that I am missing in the declaration of my macro ? Am I running a ROS version that supports this xacro default values ? Thanks in advance