--- Libc/Libc-498/string/strcat.3
+++ Libc/Libc-583/string/strcat.3
@@ -83,6 +83,9 @@
 .Fa s2 ,
 and then adds a terminating
 .Ql \e0 .
+.Pp
+The source and destination strings should not overlap, as the
+behavior is undefined.
 .Sh RETURN VALUES
 The
 .Fn strcat