Objective-C NSManagedObject shall comply with swift protocol

I would like an NSManagedObject class to comply with a protocol that I have defined in Swift.

The protocol defines only a number of properties that the NSManagedObject should have:

@objc
public protocol PLCNetworkUnit {

    var objectID: NSManagedObjectID { get }
    var type: NSNumber { get }
    var url: String { get }
    var port: NSNumber { get }
    var wifiPort: NSNumber { get }
    var wifiSSID: String { get }
    var wifiUrl: String { get }
    var modbusOffset: NSNumber { get }
}

For the most part, this works, but the compiler complains with the following warning:

'copy' attribute on property 'modbusOffset' does not match the property inherited from 'PLCNetworkUnit'

This is the definition of the NSManagedObject class:

@interface SPSStation (CoreDataProperties) <PLCNetworkUnit>

+ (NSFetchRequest<SPSStation *> *)fetchRequest;

@property (nullable, nonatomic, copy) NSNumber *activeTimeSwitches;
@property (nullable, nonatomic, copy) NSNumber *modbusOffset;
@property (nullable, nonatomic, copy) NSString *name;
@property (nullable, nonatomic, copy) NSNumber *port;
@property (nullable, nonatomic, copy) NSNumber *type;
@property (nullable, nonatomic, copy) NSString *url;
@property (nullable, nonatomic, copy) NSNumber *wifiPort;
@property (nullable, nonatomic, copy) NSString *wifiSSID;
@property (nullable, nonatomic, copy) NSString *wifiUrl;
@property (nullable, nonatomic, retain) NSSet<Gear *> *gears;
@property (nullable, nonatomic, retain) DatabaseProfile *profile;
@property (nullable, nonatomic, retain) NSSet<Program *> *programs;
@property (nullable, nonatomic, retain) NSSet<Sensor *> *sensor;
@property (nullable, nonatomic, retain) NSSet<SystemValue *> *systemValues;
@property (nullable, nonatomic, retain) NSSet<TimeSwitch *> *timer;

@end

How do I get the NSManagedObject-based class to comply with the Swift protocol without the compiler complaining?