@@ -26,10 +26,11 @@
  * @class OFGZIPStream OFGZIPStream.h ObjFW/OFGZIPStream.h
  *
  * @brief A class that handles GZIP compression and decompression transparently
  *	  for an underlying stream.
  */
+OF_SUBCLASSING_RESTRICTED
 @interface OFGZIPStream: OFStream
 {
 	OFStream *_stream;
 	OFInflateStream *_Nullable _inflateStream;
 	enum of_gzip_stream_state {