diff --git a/bamt/networks/big_brave_bn.py b/bamt/networks/big_brave_bn.py
index b6b4b1c..e4adc9a 100644
--- a/bamt/networks/big_brave_bn.py
+++ b/bamt/networks/big_brave_bn.py
@@ -28,8 +28,9 @@ def set_possible_edges_by_brave(
         Returns:
             None: Modifies the object's possible_edges attribute.
         """
-        proximity_matrix = self._get_proximity_matrix(df, proximity_metric)
-        brave_matrix = self._get_brave_matrix(df.columns, proximity_matrix, n_nearest)
+        df_copy = df.copy(deep=True)
+        proximity_matrix = self._get_proximity_matrix(df_copy, proximity_metric)
+        brave_matrix = self._get_brave_matrix(df_copy.columns, proximity_matrix, n_nearest)
 
         threshold_value = brave_matrix.max(numeric_only=True).max() * threshold
         filtered_brave_matrix = brave_matrix[brave_matrix > threshold_value].stack()