diff --git a/src/postprocessor/core/reshapers/picker.py b/src/postprocessor/core/reshapers/picker.py
index 747623eea6a16186ed53016ac66f3bd78947d77b..03d0fdc33f632b8460690522f7d07cbef85b5eab 100644
--- a/src/postprocessor/core/reshapers/picker.py
+++ b/src/postprocessor/core/reshapers/picker.py
@@ -102,8 +102,8 @@ class picker(LineageProcess):
             self.daughters = np.array([])
         else:
             self.mothers, self.daughters = (
-                tuple(self.cells.mothers_daughters[:, 1]),
-                tuple(self.cells.mothers_daughters[:, 2]),
+                list(self.cells.mothers_daughters[:, 1]),
+                list(self.cells.mothers_daughters[:, 2]),
             )
         for alg, op, *params in self.sequence:
             if indices: