diff --git a/libc/include/link.h b/libc/include/link.h
index cb8e139..e6c5404 100644
--- a/libc/include/link.h
+++ b/libc/include/link.h
@@ -46,7 +46,7 @@
   ElfW(Half) dlpi_phnum;
 };
 
-int dl_iterate_phdr(int (*)(struct dl_phdr_info*, size_t, void*), void*);
+int dl_iterate_phdr(int (*)(struct dl_phdr_info*, size_t, void*), void*) __INTRODUCED_IN(21);
 
 #ifdef __arm__
 typedef long unsigned int* _Unwind_Ptr;