diff --git a/scripts/cluster_network.py b/scripts/cluster_network.py
index 2c457bef..642db4da 100644
--- a/scripts/cluster_network.py
+++ b/scripts/cluster_network.py
@@ -263,9 +263,9 @@ def clustering_for_n_clusters(n, n_clusters, custom_busmap=False, aggregate_carr
                               algorithm="kmeans", extended_link_costs=0, focus_weights=None):
 
     if potential_mode == 'simple':
-        p_nom_max_strategy = np.sum
+        p_nom_max_strategy = pd.Series.sum
     elif potential_mode == 'conservative':
-        p_nom_max_strategy = np.min
+        p_nom_max_strategy = pd.Series.min
     else:
         raise AttributeError(f"potential_mode should be one of 'simple' or 'conservative' but is '{potential_mode}'")
 
@@ -281,7 +281,7 @@ def clustering_for_n_clusters(n, n_clusters, custom_busmap=False, aggregate_carr
         aggregate_generators_carriers=aggregate_carriers,
         aggregate_one_ports=["Load", "StorageUnit"],
         line_length_factor=line_length_factor,
-        generator_strategies={'p_nom_max': p_nom_max_strategy, 'p_nom_min': np.sum},
+        generator_strategies={'p_nom_max': p_nom_max_strategy, 'p_nom_min': pd.Series.sum},
         scale_link_capital_costs=False)
 
     if not n.links.empty: