diff --git a/sijapi/classes.py b/sijapi/classes.py
index 332f579..04eff65 100644
--- a/sijapi/classes.py
+++ b/sijapi/classes.py
@@ -489,7 +489,10 @@ class Location(BaseModel):
             datetime: lambda dt: dt.isoformat(),
         }
 
-
+    def model_dump(self):
+            data = self.dict()
+            data["datetime"] = self.datetime.isoformat() if self.datetime else None
+            return data
 
 
 class Geocoder:
diff --git a/sijapi/routers/gis.py b/sijapi/routers/gis.py
index 8d8b937..cb0daf0 100644
--- a/sijapi/routers/gis.py
+++ b/sijapi/routers/gis.py
@@ -548,11 +548,11 @@ async def get_last_location_endpoint() -> JSONResponse:
 
     if this_location:
         location_dict = this_location.model_dump()
-        location_dict["datetime"] = this_location.datetime.isoformat()
         return JSONResponse(content=location_dict)
     else:
         raise HTTPException(status_code=404, detail="No location found before the specified datetime")
 
+
 @gis.get("/locate/{datetime_str}", response_model=List[Location])
 async def get_locate(datetime_str: str, all: bool = False):
     try: