diff --git a/f1tenth_gym/envs/track/cubic_spline.py b/f1tenth_gym/envs/track/cubic_spline.py
index c14e41c9..fd61e644 100644
--- a/f1tenth_gym/envs/track/cubic_spline.py
+++ b/f1tenth_gym/envs/track/cubic_spline.py
@@ -114,7 +114,7 @@ def calc_position(self, s: float) -> tuple[Union[float, None], Union[float, None
         """
         return self.spline(s)
 
-    def calc_curvature(self, s: float) -> float | None:
+    def calc_curvature(self, s: float) -> Union[float , None]:
         """
         Calc curvature at the given s.
 
@@ -134,7 +134,7 @@ def calc_curvature(self, s: float) -> float | None:
         k = (ddy * dx - ddx * dy) / ((dx**2 + dy**2) ** (3 / 2))
         return k
 
-    def calc_yaw(self, s: float) -> float | None:
+    def calc_yaw(self, s: float) -> Union[float, None]:
         """
         Calc yaw angle at the given s.