diff --git a/KEMField/Source/Bindings/FieldSolvers/Magnetic/src/KMagfieldCoilsFieldSolverBuilder.cc b/KEMField/Source/Bindings/FieldSolvers/Magnetic/src/KMagfieldCoilsFieldSolverBuilder.cc
index 91139d27a..4f5cbc13e 100644
--- a/KEMField/Source/Bindings/FieldSolvers/Magnetic/src/KMagfieldCoilsFieldSolverBuilder.cc
+++ b/KEMField/Source/Bindings/FieldSolvers/Magnetic/src/KMagfieldCoilsFieldSolverBuilder.cc
@@ -21,8 +21,8 @@ STATICINT sKMagfieldCoilsFieldSolverStructure =
     KMagfieldCoilsFieldSolverBuilder::Attribute<string>("file") +  // coil file name
     KMagfieldCoilsFieldSolverBuilder::Attribute<bool>("replace_file") +  // write coil file
     KMagfieldCoilsFieldSolverBuilder::Attribute<bool>("force_elliptic") +
-    KMagfieldCoilsFieldSolverBuilder::Attribute<unsigned>("n_elliptic") +
-    KMagfieldCoilsFieldSolverBuilder::Attribute<unsigned>("n_max") +
+    KMagfieldCoilsFieldSolverBuilder::Attribute<int>("n_elliptic") +
+    KMagfieldCoilsFieldSolverBuilder::Attribute<int>("n_max") +
     KMagfieldCoilsFieldSolverBuilder::Attribute<double>("eps_tol");
 
 STATICINT sKStaticElectromagnetFieldStructure =