diff --git a/Device/Detector/SimulationAreaIterator.h b/Device/Detector/SimulationAreaIterator.h
index 273ea284f10c0f23c1764a714db399e58d4ef85b..3f718eebf9ba0ef4c39c194e4c3b115d9f276d56 100644
--- a/Device/Detector/SimulationAreaIterator.h
+++ b/Device/Detector/SimulationAreaIterator.h
@@ -47,7 +47,7 @@ public:
 private:
     size_t nextIndex(size_t currentIndex);
     const SimulationArea* m_area;
-    size_t m_index;         //!< global index in detector plane defined by its axes
+    size_t m_index;         //!< ROI related index
     size_t m_element_index; //!< sequential number for SimulationElementVector
 };