@@ -19,14 +19,15 @@
 
 OF_ASSUME_NONNULL_BEGIN
 
 @class OFMapTable;
 
+OF_SUBCLASSING_RESTRICTED
 @interface OFMapTableSet: OFSet
 {
 	OFMapTable *_mapTable;
 }
 
 - (instancetype)initWithCapacity: (size_t)capacity;
 @end
 
 OF_ASSUME_NONNULL_END