diff --git a/bluemira/radiation_transport/advective_transport.py b/bluemira/radiation_transport/advective_transport.py
index e66385d14f..a4d276ed17 100644
--- a/bluemira/radiation_transport/advective_transport.py
+++ b/bluemira/radiation_transport/advective_transport.py
@@ -85,7 +85,8 @@ def flux_surfaces(self) -> list[PartialOpenFluxSurface]:
 
         Returns
         -------
-        flux_surfaces: list[PartialOpenFluxSurface]
+        flux_surfaces:
+            The list of partially open flux surfaces.
         """
         flux_surfaces = []
         for group in [