diff --git a/src/server/BreCal/validators/input_validation_ship.py b/src/server/BreCal/validators/input_validation_ship.py
index c6ad45b..79c547a 100644
--- a/src/server/BreCal/validators/input_validation_ship.py
+++ b/src/server/BreCal/validators/input_validation_ship.py
@@ -110,7 +110,7 @@ class InputValidationShip():
         ships = json.loads(response)
 
         # extract only the 'imo' values
-        ship_imos = [ship.get("imo") for ship in ships if not ship.deleted]
+        ship_imos = [ship.get("imo") for ship in ships if not ship.get("deleted")]
 
         # check, if the imo in the POST-request already exists in the list
         imo_already_exists = loadedModel.get("imo") in ship_imos