diff --git a/libc/include/search.h b/libc/include/search.h
index 9b01e12..1ac6d21 100644
--- a/libc/include/search.h
+++ b/libc/include/search.h
@@ -29,17 +29,20 @@
 
 __BEGIN_DECLS
 
-void insque(void*, void*);
-void remque(void*);
+void insque(void*, void*) __INTRODUCED_IN(21);
+void remque(void*) __INTRODUCED_IN(21);
 
-void* lfind(const void*, const void*, size_t*, size_t, int (*)(const void*, const void*));
-void* lsearch(const void*, void*, size_t*, size_t, int (*)(const void*, const void*));
+void* lfind(const void*, const void*, size_t*, size_t, int (*)(const void*, const void*))
+  __INTRODUCED_IN(21);
+void* lsearch(const void*, void*, size_t*, size_t, int (*)(const void*, const void*))
+  __INTRODUCED_IN(21);
 
-void* tdelete(const void* __restrict, void** __restrict, int (*)(const void*, const void*));
-void tdestroy(void*, void (*)(void*));
-void* tfind(const void*, void* const*, int (*)(const void*, const void*));
-void* tsearch(const void*, void**, int (*)(const void*, const void*));
-void twalk(const void*, void (*)(const void*, VISIT, int));
+void* tdelete(const void* __restrict, void** __restrict, int (*)(const void*, const void*))
+  __INTRODUCED_IN(21);
+void tdestroy(void*, void (*)(void*)) __INTRODUCED_IN(21);
+void* tfind(const void*, void* const*, int (*)(const void*, const void*)) __INTRODUCED_IN(21);
+void* tsearch(const void*, void**, int (*)(const void*, const void*)) __INTRODUCED_IN(21);
+void twalk(const void*, void (*)(const void*, VISIT, int)) __INTRODUCED_IN(21);
 
 __END_DECLS