diff --git a/lib/iris/coords.py b/lib/iris/coords.py
index ff2adeac0b..c3dc45cf75 100644
--- a/lib/iris/coords.py
+++ b/lib/iris/coords.py
@@ -1711,7 +1711,7 @@ def points(self, points):
         self._values = points
 
     @property
-    def bounds(self) -> RealData:
+    def bounds(self) -> Optional[RealData]:
         """
         The coordinate bounds values, as a NumPy array,
         or None if no bound values are defined.
@@ -1837,7 +1837,7 @@ def core_points(self) -> RealOrLazyData:
         """
         return super()._core_values()
 
-    def core_bounds(self) -> RealOrLazyData:
+    def core_bounds(self) -> Optional[RealOrLazyData]:
         """
         The points array at the core of this coord, which may be a NumPy array
         or a dask array.