diff --git a/libc/include/bits/fortify/poll.h b/libc/include/bits/fortify/poll.h
index f2e27d7..1b4a5bf 100644
--- a/libc/include/bits/fortify/poll.h
+++ b/libc/include/bits/fortify/poll.h
@@ -30,9 +30,17 @@
 #error "Never include this file directly; instead, include <poll.h>"
 #endif
 
+
+#if __BIONIC_AVAILABILITY_GUARD(23)
 int __poll_chk(struct pollfd* _Nullable, nfds_t, int, size_t) __INTRODUCED_IN(23);
 int __ppoll_chk(struct pollfd* _Nullable, nfds_t, const struct timespec* _Nullable, const sigset_t* _Nullable, size_t) __INTRODUCED_IN(23);
+#endif /* __BIONIC_AVAILABILITY_GUARD(23) */
+
+
+#if __BIONIC_AVAILABILITY_GUARD(28)
 int __ppoll64_chk(struct pollfd* _Nullable, nfds_t, const struct timespec* _Nullable, const sigset64_t* _Nullable, size_t) __INTRODUCED_IN(28);
+#endif /* __BIONIC_AVAILABILITY_GUARD(28) */
+
 
 #if defined(__BIONIC_FORTIFY)
 #define __bos_fd_count_trivially_safe(bos_val, fds, fd_count)              \
diff --git a/libc/include/bits/fortify/socket.h b/libc/include/bits/fortify/socket.h
index 1c3605b..bd626f9 100644
--- a/libc/include/bits/fortify/socket.h
+++ b/libc/include/bits/fortify/socket.h
@@ -30,7 +30,11 @@
 #error "Never include this file directly; instead, include <sys/socket.h>"
 #endif
 
+
+#if __BIONIC_AVAILABILITY_GUARD(26)
 ssize_t __sendto_chk(int, const void* _Nonnull, size_t, size_t, int, const struct sockaddr* _Nullable, socklen_t) __INTRODUCED_IN(26);
+#endif /* __BIONIC_AVAILABILITY_GUARD(26) */
+
 ssize_t __recvfrom_chk(int, void* _Nullable, size_t, size_t, int, struct sockaddr* _Nullable, socklen_t* _Nullable);
 
 #if defined(__BIONIC_FORTIFY)
diff --git a/libc/include/bits/fortify/stdio.h b/libc/include/bits/fortify/stdio.h
index e4607e0..f9faeba 100644
--- a/libc/include/bits/fortify/stdio.h
+++ b/libc/include/bits/fortify/stdio.h
@@ -31,8 +31,12 @@
 #endif
 
 char* _Nullable __fgets_chk(char* _Nonnull, int, FILE* _Nonnull, size_t);
+
+#if __BIONIC_AVAILABILITY_GUARD(24)
 size_t __fread_chk(void* _Nonnull, size_t, size_t, FILE* _Nonnull, size_t) __INTRODUCED_IN(24);
 size_t __fwrite_chk(const void* _Nonnull, size_t, size_t, FILE* _Nonnull, size_t) __INTRODUCED_IN(24);
+#endif /* __BIONIC_AVAILABILITY_GUARD(24) */
+
 
 #if defined(__BIONIC_FORTIFY) && !defined(__BIONIC_NO_STDIO_FORTIFY)
 
diff --git a/libc/include/bits/fortify/string.h b/libc/include/bits/fortify/string.h
index 041967b..6f0ee4a 100644
--- a/libc/include/bits/fortify/string.h
+++ b/libc/include/bits/fortify/string.h
@@ -30,8 +30,12 @@
 #error "Never include this file directly; instead, include <string.h>"
 #endif
 
+
+#if __BIONIC_AVAILABILITY_GUARD(23)
 void* _Nullable __memchr_chk(const void* _Nonnull, int, size_t, size_t) __INTRODUCED_IN(23);
 void* _Nullable __memrchr_chk(const void* _Nonnull, int, size_t, size_t) __INTRODUCED_IN(23);
+#endif /* __BIONIC_AVAILABILITY_GUARD(23) */
+
 char* _Nonnull __stpncpy_chk2(char* _Nonnull, const char* _Nonnull, size_t, size_t, size_t);
 char* _Nonnull __strncpy_chk2(char* _Nonnull, const char* _Nonnull, size_t, size_t, size_t);
 size_t __strlcpy_chk(char* _Nonnull, const char* _Nonnull, size_t, size_t);
diff --git a/libc/include/bits/fortify/unistd.h b/libc/include/bits/fortify/unistd.h
index 7eda1a6..9acb942 100644
--- a/libc/include/bits/fortify/unistd.h
+++ b/libc/include/bits/fortify/unistd.h
@@ -29,24 +29,52 @@
 #error "Never include this file directly; instead, include <unistd.h>"
 #endif
 
-char* _Nullable __getcwd_chk(char* _Nullable, size_t, size_t) __INTRODUCED_IN(24);
 
+#if __BIONIC_AVAILABILITY_GUARD(24)
+char* _Nullable __getcwd_chk(char* _Nullable, size_t, size_t) __INTRODUCED_IN(24);
+#endif /* __BIONIC_AVAILABILITY_GUARD(24) */
+
+
+
+#if __BIONIC_AVAILABILITY_GUARD(23)
 ssize_t __pread_chk(int, void* _Nonnull, size_t, off_t, size_t) __INTRODUCED_IN(23);
+#endif /* __BIONIC_AVAILABILITY_GUARD(23) */
+
 ssize_t __pread_real(int, void* _Nonnull, size_t, off_t) __RENAME(pread);
 
+
+#if __BIONIC_AVAILABILITY_GUARD(23)
 ssize_t __pread64_chk(int, void* _Nonnull, size_t, off64_t, size_t) __INTRODUCED_IN(23);
+#endif /* __BIONIC_AVAILABILITY_GUARD(23) */
+
 ssize_t __pread64_real(int, void* _Nonnull, size_t, off64_t) __RENAME(pread64);
 
+
+#if __BIONIC_AVAILABILITY_GUARD(24)
 ssize_t __pwrite_chk(int, const void* _Nonnull, size_t, off_t, size_t) __INTRODUCED_IN(24);
+#endif /* __BIONIC_AVAILABILITY_GUARD(24) */
+
 ssize_t __pwrite_real(int, const void* _Nonnull, size_t, off_t) __RENAME(pwrite);
 
+
+#if __BIONIC_AVAILABILITY_GUARD(24)
 ssize_t __pwrite64_chk(int, const void* _Nonnull, size_t, off64_t, size_t) __INTRODUCED_IN(24);
+#endif /* __BIONIC_AVAILABILITY_GUARD(24) */
+
 ssize_t __pwrite64_real(int, const void* _Nonnull, size_t, off64_t) __RENAME(pwrite64);
 
 ssize_t __read_chk(int, void* __BIONIC_COMPLICATED_NULLNESS, size_t, size_t);
+
+#if __BIONIC_AVAILABILITY_GUARD(24)
 ssize_t __write_chk(int, const void* __BIONIC_COMPLICATED_NULLNESS, size_t, size_t) __INTRODUCED_IN(24);
+#endif /* __BIONIC_AVAILABILITY_GUARD(24) */
+
+
+#if __BIONIC_AVAILABILITY_GUARD(23)
 ssize_t __readlink_chk(const char* _Nonnull, char* _Nonnull, size_t, size_t) __INTRODUCED_IN(23);
 ssize_t __readlinkat_chk(int dirfd, const char* _Nonnull, char* _Nonnull, size_t, size_t) __INTRODUCED_IN(23);
+#endif /* __BIONIC_AVAILABILITY_GUARD(23) */
+
 
 #if defined(__BIONIC_FORTIFY)
 
diff --git a/libc/include/bits/getentropy.h b/libc/include/bits/getentropy.h
index 98d8879..c878470 100644
--- a/libc/include/bits/getentropy.h
+++ b/libc/include/bits/getentropy.h
@@ -48,6 +48,10 @@
  *
  * See also arc4random_buf() which is available in all API levels.
  */
+
+#if __BIONIC_AVAILABILITY_GUARD(28)
 __nodiscard int getentropy(void* _Nonnull __buffer, size_t __buffer_size) __INTRODUCED_IN(28);
+#endif /* __BIONIC_AVAILABILITY_GUARD(28) */
+
 
 __END_DECLS
diff --git a/libc/include/bits/lockf.h b/libc/include/bits/lockf.h
index 195b34a..8f922b9 100644
--- a/libc/include/bits/lockf.h
+++ b/libc/include/bits/lockf.h
@@ -56,6 +56,8 @@
  *
  * See also flock().
  */
+
+#if __BIONIC_AVAILABILITY_GUARD(24)
 int lockf(int __fd, int __op, off_t __length) __RENAME_IF_FILE_OFFSET64(lockf64) __INTRODUCED_IN(24);
 
 /**
@@ -63,5 +65,7 @@
  * even from a 32-bit process without `_FILE_OFFSET_BITS=64`.
  */
 int lockf64(int __fd, int __op, off64_t __length) __INTRODUCED_IN(24);
+#endif /* __BIONIC_AVAILABILITY_GUARD(24) */
+
 
 __END_DECLS
diff --git a/libc/include/bits/strcasecmp.h b/libc/include/bits/strcasecmp.h
index be910ad..d76cec9 100644
--- a/libc/include/bits/strcasecmp.h
+++ b/libc/include/bits/strcasecmp.h
@@ -51,7 +51,11 @@
 /**
  * Like strcasecmp() but taking a `locale_t`.
  */
+
+#if __BIONIC_AVAILABILITY_GUARD(23)
 int strcasecmp_l(const char* _Nonnull __s1, const char* _Nonnull __s2, locale_t _Nonnull __l) __attribute_pure__ __INTRODUCED_IN(23);
+#endif /* __BIONIC_AVAILABILITY_GUARD(23) */
+
 
 /**
  * [strncasecmp(3)](https://man7.org/linux/man-pages/man3/strncasecmp.3.html) compares the first
@@ -66,6 +70,10 @@
 /**
  * Like strncasecmp() but taking a `locale_t`.
  */
+
+#if __BIONIC_AVAILABILITY_GUARD(23)
 int strncasecmp_l(const char* _Nonnull __s1, const char* _Nonnull __s2, size_t __n, locale_t _Nonnull __l) __attribute_pure__ __INTRODUCED_IN(23);
+#endif /* __BIONIC_AVAILABILITY_GUARD(23) */
+
 
 __END_DECLS
diff --git a/libc/include/bits/wctype.h b/libc/include/bits/wctype.h
index 13a4254..d0cffec 100644
--- a/libc/include/bits/wctype.h
+++ b/libc/include/bits/wctype.h
@@ -58,8 +58,12 @@
 int iswctype(wint_t __wc, wctype_t __type);
 
 typedef const void* wctrans_t;
+
+#if __BIONIC_AVAILABILITY_GUARD(26)
 wint_t towctrans(wint_t __wc, wctrans_t _Nonnull __transform) __INTRODUCED_IN(26);
 wctrans_t _Nullable wctrans(const char* _Nonnull __name) __INTRODUCED_IN(26);
+#endif /* __BIONIC_AVAILABILITY_GUARD(26) */
+
 
 __END_DECLS