what must be defined for axisymmetric study

Hello,

in CAELinux 2007, I try to do a model for a cylinder in rotation.
I have created a geometry with 5 vertices (1 for the origin and 4 to define the section of the cylinder) and a quadrangle.
I have created a mesh.

With the Code Aster Wizards, I have selected Isotropic Linear Elasticity Study, Axisymmetric model. Now when I try to select the quadrangle face in the geometry as the main shape, I get this error message :

No sub-shape from the selected shape exist, or does match with this kind of modelisation.

What did I miss ? What must be defined to do this kind of study ?

Thanks for any help,

Joseph