diff --git a/geomagio/api/ws/observatories.py b/geomagio/api/ws/observatories.py
index 4e433dae25ccb1410d79a6811225ac46bd4f364c..9a34e985033cd484cbbaf5a96b023710aa4a17e0 100644
--- a/geomagio/api/ws/observatories.py
+++ b/geomagio/api/ws/observatories.py
@@ -35,7 +35,7 @@ def get_observatories() -> Dict:
 
 
 @router.get("/observatories/{id}")
-async def get_observatory_by_id(id: str):
+async def get_observatory_by_id(id: str) -> Dict:
     for o in OBSERVATORIES:
         if o.id == id:
             return {