diff --git a/FDTD/operator_cylindermultigrid.cpp b/FDTD/operator_cylindermultigrid.cpp
index 3dbaae4..f8ecee5 100644
--- a/FDTD/operator_cylindermultigrid.cpp
+++ b/FDTD/operator_cylindermultigrid.cpp
@@ -148,12 +148,24 @@ void Operator_CylinderMultiGrid::SetTag(int tag)
 
 void Operator_CylinderMultiGrid::SetNeighborUp(int ny, int id)
 {
+	if (ny==0)
+	{
+		cerr << "Operator_CylinderMultiGrid::SetNeighborUp: Error: MPI segregation in radial direction not supported for a cylindircal multigrid. Exit!";
+		MPI_Barrier(MPI_COMM_WORLD);
+		exit(-1);
+	}
 	Operator_Cylinder::SetNeighborUp(ny,id);
 	m_InnerOp->SetNeighborUp(ny,id);
 }
 
 void Operator_CylinderMultiGrid::SetNeighborDown(int ny, int id)
 {
+	if (ny==0)
+	{
+		cerr << "Operator_CylinderMultiGrid::SetNeighborDown: Error: MPI segregation in radial direction not supported for a cylindircal multigrid. Exit!";
+		MPI_Barrier(MPI_COMM_WORLD);
+		exit(-1);
+	}
 	Operator_Cylinder::SetNeighborDown(ny,id);
 	m_InnerOp->SetNeighborDown(ny,id);
 }
diff --git a/FDTD/operator_mpi.cpp b/FDTD/operator_mpi.cpp
index 121f560..0d6635c 100644
--- a/FDTD/operator_mpi.cpp
+++ b/FDTD/operator_mpi.cpp
@@ -60,7 +60,6 @@ double Operator_MPI::CalcTimestep()
 	return ret;
 }
 
-
 void Operator_MPI::SetBoundaryCondition(int* BCs)
 {
 	if (!m_MPI_Enabled)