@@ -22,9 +22,10 @@
 /*!
  * @class OFSHA256Hash OFSHA256Hash.h ObjFW/OFSHA256Hash.h
  *
  * @brief A class which provides methods to create an SHA-256 hash.
  */
+OF_SUBCLASSING_RESTRICTED
 @interface OFSHA256Hash: OFSHA224Or256Hash
 @end
 
 OF_ASSUME_NONNULL_END