diff --git a/FDTD/extensions/operator_ext_conductingsheet.cpp b/FDTD/extensions/operator_ext_conductingsheet.cpp
index b7efca5..5f82cbf 100644
--- a/FDTD/extensions/operator_ext_conductingsheet.cpp
+++ b/FDTD/extensions/operator_ext_conductingsheet.cpp
@@ -25,6 +25,18 @@ Operator_Ext_ConductingSheet::Operator_Ext_ConductingSheet(Operator* op, double
 	m_f_max = f_max;
 }
 
+Operator_Ext_ConductingSheet::Operator_Ext_ConductingSheet(Operator* op, Operator_Ext_ConductingSheet* op_ext) : Operator_Ext_LorentzMaterial(op, op_ext)
+{
+	m_f_max = op_ext->m_f_max;
+}
+
+Operator_Extension* Operator_Ext_ConductingSheet::Clone(Operator* op)
+{
+	if (dynamic_cast<Operator_Ext_ConductingSheet*>(this)==NULL)
+		return NULL;
+	return new Operator_Ext_ConductingSheet(op, this);
+}
+
 bool Operator_Ext_ConductingSheet::BuildExtension()
 {
 	double dT = m_Op->GetTimestep();
diff --git a/FDTD/extensions/operator_ext_conductingsheet.h b/FDTD/extensions/operator_ext_conductingsheet.h
index 7efdea3..9bd5200 100644
--- a/FDTD/extensions/operator_ext_conductingsheet.h
+++ b/FDTD/extensions/operator_ext_conductingsheet.h
@@ -32,6 +32,8 @@ class Operator_Ext_ConductingSheet : public Operator_Ext_LorentzMaterial
 public:
 	Operator_Ext_ConductingSheet(Operator* op, double f_max);
 
+	virtual Operator_Extension* Clone(Operator* op);
+
 	virtual bool BuildExtension();
 
 	virtual bool IsCylinderCoordsSave(bool closedAlpha, bool R0_included) const {return true;}
@@ -40,6 +42,8 @@ public:
 	virtual string GetExtensionName() const {return string("Conducting Sheet Extension");}
 
 protected:
+	//! Copy constructor
+	Operator_Ext_ConductingSheet(Operator* op, Operator_Ext_ConductingSheet* op_ext);
 	double m_f_max;
 };