diff --git a/Magnetodynamics/transfo.pro b/Magnetodynamics/transfo.pro
index abeeed7b0be6f393b0cb342b7b428d85fae3d588..4e162b010d69bd44351f900ec754fd929a8cebe4 100644
--- a/Magnetodynamics/transfo.pro
+++ b/Magnetodynamics/transfo.pro
@@ -23,6 +23,8 @@ DefineConstant[
     Name "Parameters/01Conductor type"}
   Freq = {1, Min 0, Max 1e3, Step 1,
     Name "Parameters/Frequency"}
+  mur_Core = {1000, Min 1, Max 10000, Step 1,
+    Name "Parameters/Core relative permeability"}
 ];
 
 Group {
@@ -50,7 +52,6 @@ Group {
 
 Function {
   mu0 = 4e-7*Pi;
-  mur_Core = 1000;
   mu[Air] = 1 * mu0;
   mu[Core] = mur_Core * mu0;
   mu[Coils] = 1 * mu0;