diff --git a/RecCalorimeter/src/components/CreateCaloClustersSlidingWindow.h b/RecCalorimeter/src/components/CreateCaloClustersSlidingWindow.h
index 6ef7836b..c945c9db 100644
--- a/RecCalorimeter/src/components/CreateCaloClustersSlidingWindow.h
+++ b/RecCalorimeter/src/components/CreateCaloClustersSlidingWindow.h
@@ -14,13 +14,6 @@ namespace edm4hep {
 class ClusterCollection;
 }
 
-// Cluster
-struct cluster {
-  float transEnergy;
-  float eta;
-  float phi;
-};
-
 /** @class CreateCaloClustersSlidingWindow
  *
  *  Algorithm for creating calorimeter clusters from cells.
@@ -81,6 +74,13 @@ class CreateCaloClustersSlidingWindow : public GaudiAlgorithm {
   StatusCode finalize();
 
 private:
+  // Cluster
+  struct cluster {
+    float transEnergy;
+    float eta;
+    float phi;
+  };
+
   /**  Correct way to access the neighbour of the phi tower, taking into account the full coverage in phi.
    *   Full coverage means that first tower in phi, with ID = 0 is a direct neighbour
    *   of the last tower in phi with ID = m_nPhiTower - 1).