@@ -17,12 +17,13 @@
 
 #import "OFValue.h"
 
 OF_ASSUME_NONNULL_BEGIN
 
+OF_SUBCLASSING_RESTRICTED
 @interface OFNonretainedObjectValue: OFValue
 {
 	id _object;
 }
 @end
 
 OF_ASSUME_NONNULL_END