diff --git a/headers/posix/stdio.h b/headers/posix/stdio.h
index b5fa277f30..7f876f27cb 100644
--- a/headers/posix/stdio.h
+++ b/headers/posix/stdio.h
@@ -99,6 +99,17 @@ extern void		perror(const char *errorPrefix);
 extern FILE		*fmemopen(void *buf, size_t size, const char *mode);
 extern FILE		*open_memstream(char **buf, size_t *size);
 
+/* callback streams */
+#ifdef _GNU_SOURCE
+typedef struct {
+	cookie_read_function_t  *read;
+	cookie_write_function_t *write;
+	cookie_seek_function_t  *seek;
+	cookie_close_function_t *close;
+} cookie_io_functions_t;
+extern FILE		*fopencookie(void *cookie, const char *mode, cookie_io_functions_t io_funcs);
+#endif /*_GNU_SOURCE*/
+
 /* file I/O */
 extern int		fflush(FILE *stream);
 extern int		fflush_unlocked(FILE *stream);