diff --git a/bind/G4Calo.py b/bind/G4Calo.py
index 53b7edf..2a2c601 100644
--- a/bind/G4Calo.py
+++ b/bind/G4Calo.py
@@ -401,5 +401,5 @@ def display_event(gd : GeometryDescriptor,
 
 
 
-def to_numpy(df_column):
-    return np.array(df_column.tolist())
\ No newline at end of file
+def to_numpy(df_column, dtype=None):
+    return np.array(df_column.tolist(), dtype=dtype)
\ No newline at end of file