diff --git a/tardis/io/atom_data/base.py b/tardis/io/atom_data/base.py
index 40acbe0b233..1c901f523a9 100644
--- a/tardis/io/atom_data/base.py
+++ b/tardis/io/atom_data/base.py
@@ -449,7 +449,8 @@ def prepare_lines(self):
             )
         ]
 
-        self.lines = self.lines.sort_values(by="wavelength")
+        # self.lines = self.lines.sort_values(by="wavelength")
+        self.lines = self.lines.sort_values(by=["wavelength"], kind="mergesort")
 
     def prepare_line_level_indexes(self):
         levels_index = pd.Series(
diff --git a/tardis/transport/montecarlo/tests/test_rpacket_tracker.py b/tardis/transport/montecarlo/tests/test_rpacket_tracker.py
index 971183d2360..49d449057e9 100644
--- a/tardis/transport/montecarlo/tests/test_rpacket_tracker.py
+++ b/tardis/transport/montecarlo/tests/test_rpacket_tracker.py
@@ -138,7 +138,7 @@ def test_boundary_interactions(rpacket_tracker, regression_data):
     # Hard coding the number of columns
     # Based on the largest size of boundary_interaction array (60)
     obtained_boundary_interaction = np.full(
-        (no_of_packets, 64),
+        (no_of_packets, 77),
         [-1],
         dtype=rpacket_tracker[0].boundary_interaction.dtype,
     )