diff --git a/src/roll_rate_analysis/mom_roll_rate_table.py b/src/roll_rate_analysis/mom_roll_rate_table.py
index 941b316..23196f7 100644
--- a/src/roll_rate_analysis/mom_roll_rate_table.py
+++ b/src/roll_rate_analysis/mom_roll_rate_table.py
@@ -101,7 +101,11 @@ def build(self):
         )
 
     def _get_temp_data(
-        self, data: pl.DataFrame, case: int, cycle: int = None, priority: int = None
+        self,
+        data: pl.DataFrame,
+        case: int,
+        cycle: int | None = None,
+        priority: int | None = None,
     ):
         """
         Get a temporary grouped part of the data, for every step of the roll rate calculation procedure.
diff --git a/src/roll_rate_analysis/snapshot_roll_rate_table.py b/src/roll_rate_analysis/snapshot_roll_rate_table.py
index c62c00e..96a3195 100644
--- a/src/roll_rate_analysis/snapshot_roll_rate_table.py
+++ b/src/roll_rate_analysis/snapshot_roll_rate_table.py
@@ -52,7 +52,7 @@ def __init__(
         delinquency_col: str,
         obs_files: list[str],
         perf_files: list[str],
-        keep_cols: list[str] = None,
+        keep_cols: list[str] | None = None,
         max_delq: int = 6,
         detailed: bool = False,
         granularity: int = 1,