@@ -38,11 +38,11 @@
 @property (readonly, nonatomic) OFKernelEventObserver *observer;
 
 /*!
  * The errno of the error that occurred.
  */
-@property (readonly) int errNo;
+@property (readonly, nonatomic) int errNo;
 
 + (instancetype)exception OF_UNAVAILABLE;
 
 /*!
  * @brief Creates a new, autoreleased observe failed exception.