@@ -15,10 +15,12 @@
  */
 
 #import "OFObject.h"
 
 #import "socket.h"
+
+OF_ASSUME_NONNULL_BEGIN
 
 @class OFMutableArray OF_GENERIC(ObjectType);
 @class OFMutableDictionary OF_GENERIC(KeyType, ObjectType);
 @class OFDataArray;
 #ifdef OF_HAVE_THREADS
@@ -125,11 +127,11 @@
 	OFMutex *_mutex;
 #endif
 }
 
 #ifdef OF_HAVE_PROPERTIES
-@property (assign) id <OFKernelEventObserverDelegate> delegate;
+@property (assign, nullable) id <OFKernelEventObserverDelegate> delegate;
 #endif
 
 /*!
  * @brief Creates a new OFKernelEventObserver.
  *
@@ -140,18 +142,18 @@
 /*!
  * @brief Returns the delegate for the OFKernelEventObserver.
  *
  * @return The delegate for the OFKernelEventObserver
  */
-- (id <OFKernelEventObserverDelegate>)delegate;
+- (nullable id <OFKernelEventObserverDelegate>)delegate;
 
 /*!
  * @brief Sets the delegate for the OFKernelEventObserver.
  *
  * @param delegate The delegate for the OFKernelEventObserver
  */
-- (void)setDelegate: (id <OFKernelEventObserverDelegate>)delegate;
+- (void)setDelegate: (nullable id <OFKernelEventObserverDelegate>)delegate;
 
 /*!
  * @brief Adds an object to observe for reading.
  *
  * This is also used to observe a listening socket for incoming connections,
@@ -226,5 +228,7 @@
 @end
 
 @interface OFObject (OFKernelEventObserverDelegate)
     <OFKernelEventObserverDelegate>
 @end
+
+OF_ASSUME_NONNULL_END