@@ -17,12 +17,13 @@
 
 #import "OFValue.h"
 
 OF_ASSUME_NONNULL_BEGIN
 
+OF_SUBCLASSING_RESTRICTED
 @interface OFRectangleValue: OFValue
 {
 	of_rectangle_t _rectangle;
 }
 @end
 
 OF_ASSUME_NONNULL_END