diff --git a/FDTD/openems_fdtd_mpi.cpp b/FDTD/openems_fdtd_mpi.cpp
index fd7e0cc..27b5b82 100644
--- a/FDTD/openems_fdtd_mpi.cpp
+++ b/FDTD/openems_fdtd_mpi.cpp
@@ -118,10 +118,12 @@ bool openEMS_FDTD_MPI::SetupMPI(TiXmlElement* FDTD_Opts)
 
 		//lower neighbor is ID-1
 		if (m_MyID>0)
-			m_MPI_Op->m_NeighborDown[2]=m_MyID-1;
+			m_MPI_Op->SetNeighborDown(2,m_MyID-1);
 		//upper neighbor is ID+1
 		if (m_MyID<m_NumProc-1)
-			m_MPI_Op->m_NeighborUp[2]=m_MyID+1;
+			m_MPI_Op->SetNeighborUp(2,m_MyID+1);
+
+		m_MPI_Op->SetTag(0);
 	}
 	else
 		cerr << "openEMS_FDTD_MPI::SetupMPI: Warning: Number of MPI processes is 1, skipping MPI engine... " << endl;
diff --git a/FDTD/operator_mpi.cpp b/FDTD/operator_mpi.cpp
index 68a5f02..f299205 100644
--- a/FDTD/operator_mpi.cpp
+++ b/FDTD/operator_mpi.cpp
@@ -99,6 +99,20 @@ Engine* Operator_MPI::CreateEngine() const
 		return Engine_SSE_Compressed::New(this);
 }
 
+void Operator_MPI::SetNeighborUp(int ny, int id)
+{
+	if ((ny<0) || (ny>2))
+		return;
+	m_NeighborUp[ny]=id;
+}
+
+void Operator_MPI::SetNeighborDown(int ny, int id)
+{
+	if ((ny<0) || (ny>2))
+		return;
+	m_NeighborDown[ny]=id;
+}
+
 void Operator_MPI::Init()
 {
 	Operator_SSE_Compressed::Init();
diff --git a/FDTD/operator_mpi.h b/FDTD/operator_mpi.h
index f480868..1fd4d95 100644
--- a/FDTD/operator_mpi.h
+++ b/FDTD/operator_mpi.h
@@ -23,7 +23,6 @@
 class Operator_MPI : public Operator_SSE_Compressed
 {
 	friend class Engine_MPI;
-	friend class openEMS_FDTD_MPI;
 public:
 	//! Create a new operator
 	static Operator_MPI* New();
@@ -36,6 +35,11 @@ public:
 
 	virtual Engine* CreateEngine() const;
 
+	virtual void SetTag(int tag) {m_MyTag=tag;}
+
+	virtual void SetNeighborUp(int ny, int id);
+	virtual void SetNeighborDown(int ny, int id);
+
 protected:
 	Operator_MPI();
 	bool m_MPI_Enabled;