diff --git a/openems.cpp b/openems.cpp
index 720149e..e8e3dcc 100644
--- a/openems.cpp
+++ b/openems.cpp
@@ -266,10 +266,11 @@ int openEMS::SetupFDTD(const char* file)
 	{
 		FDTD_Op->DumpMaterial2File("material_dump.vtk");
 	}
-	if (DebugOp)
-	{
+	if (DebugOp && (m_engine == EngineType_Standard))
 		FDTD_Op->DumpOperator2File("operator_dump.vtk");
-	}
+	if (DebugOp && (m_engine != EngineType_Standard))
+		cerr << "openEMS - Warning: operator dump needs the standard engine." << endl;
+
 
 	time_t OpDoneTime=time(NULL);