@@ -33,13 +33,14 @@
 /*!
  * @class OFConstantString OFConstantString.h ObjFW/OFConstantString.h
  *
  * @brief A class for storing constant strings using the `@""` literal.
  */
+OF_SUBCLASSING_RESTRICTED
 @interface OFConstantString: OFString
 {
 	char *_cString;
 	unsigned int _cStringLength;
 }
 @end
 
 OF_ASSUME_NONNULL_END