diff --git a/superblockify/metrics/measures.py b/superblockify/metrics/measures.py
index 2c75200..5c32d37 100644
--- a/superblockify/metrics/measures.py
+++ b/superblockify/metrics/measures.py
@@ -167,9 +167,9 @@ def calculate_coverage(partitioner, weight):
     if partitioner.graph.number_of_edges() == partitioner.sparsified.number_of_edges():
         return 0
 
-    return 1 - npsum(
+    return 1 - sum(
         d[weight] for u, v, d in partitioner.sparsified.edges(data=True)
-    ) / npsum(d[weight] for u, v, d in partitioner.graph.edges(data=True))
+    ) / sum(d[weight] for u, v, d in partitioner.graph.edges(data=True))
 
 
 def rel_increase(value_i, value_j):
diff --git a/superblockify/partitioning/utils.py b/superblockify/partitioning/utils.py
index 20f39d5..097288f 100644
--- a/superblockify/partitioning/utils.py
+++ b/superblockify/partitioning/utils.py
@@ -272,10 +272,12 @@ def show_highway_stats(graph):
         "Dtype counts (type, count, proportion): \n%s", dtype_counts.to_string()
     )
     # Warning if 'str' is underrepresented
-    if dtype_counts.loc[dtype_counts.index == str, "proportion"].values < 0.98:
+    str_proportion_series = dtype_counts.loc[dtype_counts.index == str, "proportion"]
+    str_proportion = str_proportion_series.iloc[0] if not str_proportion_series.empty else 0.0
+    if str_proportion < 0.98:
         logger.warning(
             "The dtype of the 'highway' attribute is not 'str' in %d%% of the edges.",
-            (1 - dtype_counts.loc[dtype_counts.index == str, "proportion"]) * 100,
+            int((1 - str_proportion) * 100),
         )