diff --git a/src/server/BreCal/validators/input_validation_ship.py b/src/server/BreCal/validators/input_validation_ship.py
index ce1c5e4..af9855b 100644
--- a/src/server/BreCal/validators/input_validation_ship.py
+++ b/src/server/BreCal/validators/input_validation_ship.py
@@ -6,7 +6,7 @@ from marshmallow import ValidationError
 from string import ascii_letters, digits
 
 from BreCal.schemas.model import Ship, Shipcall, Berth, User, Participant, ShipcallType
-from BreCal.database.sql_handler import execute_sql_query_standalone    
+from BreCal.database.sql_handler import execute_sql_query_standalone
 from BreCal.database.sql_queries import SQLQuery
 from BreCal.impl.participant import GetParticipant
 from BreCal.impl.ships import GetShips
@@ -27,7 +27,7 @@ class InputValidationShip():
     Example:
         InputValidationShip.evaluate(user_data, loadedModel, content)
 
-    When the data violates one of the rules, a marshmallow.ValidationError is raised, which details the issues. 
+    When the data violates one of the rules, a marshmallow.ValidationError is raised, which details the issues.
     """
     def __init__(self) -> None:
         pass
@@ -37,13 +37,13 @@ class InputValidationShip():
         # 1.) Only users of type BSMD are allowed to POST
         InputValidationShip.check_user_is_bsmd_type(user_data)
 
-        # 2.) The ship IMOs are used as matching keys. They must be unique in the database. 
+        # 2.) The ship IMOs are used as matching keys. They must be unique in the database.
         InputValidationShip.check_ship_imo_already_exists(loadedModel)
 
         # 3.) Check for reasonable Values (see BreCal.schemas.model.ShipSchema)
         InputValidationShip.optionally_evaluate_bollard_pull_value(content)
         return
-    
+
     @staticmethod
     def evaluate_put_data(user_data:dict, loadedModel:dict, content:dict):
         # 1.) Only users of type BSMD are allowed to PUT
@@ -58,20 +58,20 @@ class InputValidationShip():
         # 4.) Check for reasonable Values (see BreCal.schemas.model.ShipSchema)
         InputValidationShip.optionally_evaluate_bollard_pull_value(content)
         return
-    
+
     @staticmethod
     def evaluate_delete_data(user_data:dict, ship_id:typing.Optional[int]):
         if ship_id is None:
             raise ValidationError({"id":f"The ship id must be provided."})
         ship_id = int(ship_id)
-        
+
         # 1.) Only users of type BSMD are allowed to PUT
         InputValidationShip.check_user_is_bsmd_type(user_data)
 
         # 2.) The dataset entry may not be deleted already
         InputValidationShip.check_if_entry_is_already_deleted(ship_id)
         return
-    
+
     @staticmethod
     def optionally_evaluate_bollard_pull_value(content:dict):
         bollard_pull = content.get("bollard_pull",None)
@@ -89,7 +89,7 @@ class InputValidationShip():
         is_bsmd = check_if_user_is_bsmd_type(user_data)
         if not is_bsmd:
             raise ValidationError({"participant_type":f"current user does not belong to BSMD. Cannot post, put or delete ships. Found user data: {user_data}"})
-        
+
     @staticmethod
     def check_ship_imo_already_exists(loadedModel:dict):
         # get the ships, convert them to a list of JSON dictionaries
@@ -97,35 +97,35 @@ 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
         if imo_already_exists:
             raise ValidationError({"imo":f"the provided ship IMO {loadedModel.get('imo')} already exists. A ship may only be added, if there is no other ship with the same IMO number."})
         return
-    
+
     @staticmethod
     def put_content_may_not_contain_imo_number(content:dict):
         # IMO is a required field, so it will never be None outside of tests. If so, there is no violation
         put_data_ship_imo = content.get("imo",None)
         if put_data_ship_imo is None:
             return
-        
+
         # grab the ship by its ID and compare, whether the IMO is unchanged
         ship = execute_sql_query_standalone(SQLQuery.get_ship_by_id(), param={"id":content.get("id")}, command_type="single", model=Ship)
 
         if put_data_ship_imo != ship.imo:
             raise ValidationError({"imo":f"The IMO number field may not be changed since it serves the purpose of a primary (matching) key."})
         return
-    
+
     @staticmethod
     def content_contains_ship_id(content:dict):
         put_data_ship_id = content.get('id',None)
         if put_data_ship_id is None:
             raise ValidationError({"id":f"The id field is required."})
         return
-    
+
     @staticmethod
     def check_if_entry_is_already_deleted(ship_id:typing.Optional[int]):
         """
@@ -147,4 +147,4 @@ class InputValidationShip():
         return
 
 
-            
+