diff --git a/src/db/db/dbHierNetworkProcessor.cc b/src/db/db/dbHierNetworkProcessor.cc
index 315095ed2..53a1870e8 100644
--- a/src/db/db/dbHierNetworkProcessor.cc
+++ b/src/db/db/dbHierNetworkProcessor.cc
@@ -472,7 +472,7 @@ template class DB_PUBLIC local_clusters<db::PolygonRef>;
 
 template <class T>
 const typename connected_clusters<T>::connections_type &
-connected_clusters<T>::connections_for_cluster (typename local_cluster<T>::id_type id)
+connected_clusters<T>::connections_for_cluster (typename local_cluster<T>::id_type id) const
 {
   typename std::map<typename local_cluster<T>::id_type, connections_type>::const_iterator c = m_connections.find (id);
   if (c == m_connections.end ()) {
@@ -532,6 +532,9 @@ connected_clusters<T>::find_cluster_with_connection (const ClusterInstance &ci,
   return 0;
 }
 
+//  explicit instantiations
+template class DB_PUBLIC connected_clusters<db::PolygonRef>;
+
 // ------------------------------------------------------------------------------
 //  connected_clusters implementation
 
diff --git a/src/db/db/dbHierNetworkProcessor.h b/src/db/db/dbHierNetworkProcessor.h
index df7b37af0..3964cc76b 100644
--- a/src/db/db/dbHierNetworkProcessor.h
+++ b/src/db/db/dbHierNetworkProcessor.h
@@ -391,7 +391,7 @@ public:
   /**
    *  @brief Gets the connections for a given cluster ID
    */
-  const connections_type &connections_for_cluster (typename local_cluster<T>::id_type id);
+  const connections_type &connections_for_cluster (typename local_cluster<T>::id_type id) const;
 
   /**
    *  @brief Adds a connection between a local cluster and one from a child instance
@@ -414,7 +414,6 @@ public:
 
 private:
   std::map<typename local_cluster<T>::id_type, connections_type> m_connections;
-  box_type m_full_bbox;
 };
 
 template <typename> class cell_clusters_box_converter;
diff --git a/src/db/unit_tests/dbHierNetworkProcessorTests.cc b/src/db/unit_tests/dbHierNetworkProcessorTests.cc
index 4cc87f51a..c3911ed38 100644
--- a/src/db/unit_tests/dbHierNetworkProcessorTests.cc
+++ b/src/db/unit_tests/dbHierNetworkProcessorTests.cc
@@ -323,3 +323,72 @@ TEST(20_LocalClustersBasic)
   );
 }
 
+TEST(30_LocalConnectedClusters)
+{
+  db::Layout layout;
+  db::cell_index_type ci1 = layout.add_cell ("C1");
+  db::cell_index_type ci2 = layout.add_cell ("C2");
+  db::cell_index_type ci3 = layout.add_cell ("C3");
+
+  db::Instance i1 = layout.cell (ci1).insert (db::CellInstArray (db::CellInst (ci2), db::Trans ()));
+  db::Instance i2 = layout.cell (ci2).insert (db::CellInstArray (db::CellInst (ci3), db::Trans ()));
+
+  db::connected_clusters<db::PolygonRef> cc;
+
+  db::ClusterInstance::inst_path_type p1;
+  p1.push_back (db::InstElement (i1));
+
+  db::ClusterInstance::inst_path_type p2;
+  p2.push_back (db::InstElement (i1));
+  p2.push_back (db::InstElement (i2));
+
+  db::ClusterInstance::inst_path_type p3;
+  p3.push_back (db::InstElement (i2));
+
+  db::connected_clusters<db::PolygonRef>::connections_type x;
+  db::connected_clusters<db::PolygonRef>::connections_type::const_iterator ix;
+
+  x = cc.connections_for_cluster (1);
+  EXPECT_EQ (x.size (), size_t (0));
+  x = cc.connections_for_cluster (2);
+  EXPECT_EQ (x.size (), size_t (0));
+
+  cc.add_connection (1, db::ClusterInstance (1, p1));
+  cc.add_connection (1, db::ClusterInstance (2, p2));
+
+  x = cc.connections_for_cluster (1);
+  EXPECT_EQ (x.size (), size_t (2));
+  x = cc.connections_for_cluster (2);
+  EXPECT_EQ (x.size (), size_t (0));
+
+  cc.add_connection (2, db::ClusterInstance (1, p2));
+  x = cc.connections_for_cluster (2);
+  EXPECT_EQ (x.size (), size_t (1));
+
+  cc.join_connected_clusters (1, 2);
+  x = cc.connections_for_cluster (1);
+  EXPECT_EQ (x.size (), size_t (3));
+  ix = x.begin ();
+  EXPECT_EQ (ix->id (), size_t (1));
+  EXPECT_EQ (ix->inst () == p1, true);
+  ++ix;
+  EXPECT_EQ (ix->id (), size_t (2));
+  EXPECT_EQ (ix->inst () == p2, true);
+  ++ix;
+  EXPECT_EQ (ix->id (), size_t (1));
+  EXPECT_EQ (ix->inst () == p2, true);
+
+  x = cc.connections_for_cluster (2);
+  EXPECT_EQ (x.size (), size_t (0));
+
+  cc.add_connection (2, db::ClusterInstance (3, p1));
+
+  EXPECT_EQ (cc.find_cluster_with_connection (db::ClusterInstance (3, p1), 0), 2);
+  EXPECT_EQ (cc.find_cluster_with_connection (db::ClusterInstance (2, p1), 0), 0);
+  EXPECT_EQ (cc.find_cluster_with_connection (db::ClusterInstance (2, p2), 0), 1);
+
+  cc.add_connection (17, db::ClusterInstance (2, p3));
+
+  //  p3 == p2 minus 1 at the beginning
+  EXPECT_EQ (cc.find_cluster_with_connection (db::ClusterInstance (2, p2), 1 /*one stripped*/), 17);
+}