diff --git a/Electrostatics/microstrip.geo b/Electrostatics/microstrip.geo
index 04ecbf515d566ca77ed14566b1be84e24bb52706..51dbe5d123487014117677e94377c8638b9d0abf 100644
--- a/Electrostatics/microstrip.geo
+++ b/Electrostatics/microstrip.geo
@@ -15,7 +15,8 @@ xBox = w/2. * 6. ;  yBox = h * 12. ;
 
 /* Definition of parameters for local mesh dimensions */
 
-s = 1. ;
+DefineConstant[ s = {1., Name "Parameters/Global mesh size factor"} ] ;
+
 p0 = h / 10. * s ;
 pLine0 = w/2. / 10. * s ;  pLine1 = w/2. / 50. * s ;
 pxBox = xBox / 10. * s ;  pyBox = yBox / 8. * s ;