diff --git a/include/unistd.h b/include/unistd.h
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -326,6 +326,9 @@
 __BEGIN_DECLS
 /* 1003.1-1990 */
 void	 _exit(int) __dead2;
+#if __POSIX_VISIBLE >= 202405
+pid_t	 _Fork(void);
+#endif
 int	 access(const char *, int);
 unsigned int	 alarm(unsigned int);
 int	 chdir(const char *);
@@ -595,7 +598,6 @@
 int	 unwhiteout(const char *);
 void	*valloc(size_t);			/* obsoleted by malloc() */
 int	 funlinkat(int, const char *, int, int);
-pid_t	 _Fork(void);
 
 #ifndef _OPTRESET_DECLARED
 #define	_OPTRESET_DECLARED
diff --git a/lib/libsys/fork.2 b/lib/libsys/fork.2
--- a/lib/libsys/fork.2
+++ b/lib/libsys/fork.2
@@ -138,6 +138,7 @@
 or
 .Xr rtld 1 )
 are available in the child if forked from multi-threaded parent.
+.Pp
 In particular, if using dynamic linking, all dynamic symbols used by the
 child after
 .Fn _Fork
@@ -151,6 +152,7 @@
 or by using each symbol before the
 .Fn _Fork
 call to force the binding.
+Either of the methods subtly changes the ABI of the resulting binary.
 .Sh RETURN VALUES
 Upon successful completion,
 .Fn fork