@@ -204,10 +204,11 @@
 	size_t _readBufferLength, _writeBufferLength;
 	bool _writeBuffered, _waitingForDelimiter;
 @protected
 	bool _blocking;
 	id _Nullable _delegate;
+	OF_RESERVE_IVARS(4)
 }
 
 /*!
  * @brief Whether the end of the stream has been reached.
  */