diff --git a/smarts/core/utils/sumo.py b/smarts/core/utils/sumo.py
index 263dda72ec..2f162c295a 100644
--- a/smarts/core/utils/sumo.py
+++ b/smarts/core/utils/sumo.py
@@ -242,7 +242,7 @@ def port(self) -> Optional[int]:
         return self._sumo_port
 
     @property
-    def hostname(self) -> Optional[int]:
+    def hostname(self) -> str:
         """Get the used TraCI port."""
         return self._host