diff --git a/evofr/data/hier_frequencies.py b/evofr/data/hier_frequencies.py
index 5af17c0..8a470b7 100644
--- a/evofr/data/hier_frequencies.py
+++ b/evofr/data/hier_frequencies.py
@@ -57,6 +57,14 @@ def __init__(
         self.var_names = format_var_names(raw_var_names, pivot=pivot)
         self.pivot = self.var_names[-1]
 
+        # Loop each group
+        grouped = raw_seq.groupby(group)
+        self.names = [name for name, _ in grouped]
+        self.groups = [
+            VariantFrequencies(group, self.date_to_index, self.var_names)
+            for _, group in grouped
+        ]
+
         # Aggregate counts into larger windows
         self.aggregation_frequency = aggregation_frequency
         if self.aggregation_frequency is not None:
@@ -68,14 +76,6 @@ def __init__(
                 self.groups, self.dates, self.aggregation_frequency
             )
 
-        # Loop each group
-        grouped = raw_seq.groupby(group)
-        self.names = [name for name, _ in grouped]
-        self.groups = [
-            VariantFrequencies(group, self.date_to_index, self.var_names)
-            for _, group in grouped
-        ]
-
         self.seq_counts = np.stack([g.seq_counts for g in self.groups], axis=-1)
 
     def make_data_dict(self, data: Optional[dict] = None) -> dict: