@@ -19,13 +19,14 @@
 
 OF_ASSUME_NONNULL_BEGIN
 
 @class OFMutableData;
 
+OF_SUBCLASSING_RESTRICTED
 @interface OFMutableAdjacentArray: OFMutableArray
 {
 	OFMutableData *_array;
 	unsigned long _mutations;
 }
 @end
 
 OF_ASSUME_NONNULL_END