diff --git a/man2/seteuid.2 b/man2/seteuid.2
index d923ef7ba..c64cb493c 100644
--- a/man2/seteuid.2
+++ b/man2/seteuid.2
@@ -69,6 +69,13 @@ On success, zero is returned.
 On error, \-1 is returned, and
 .I errno
 is set appropriately.
+
+.IR Note :
+there are cases where
+.BR seteuid ()
+can fail even when the caller is UID 0;
+it is a grave security error to omit checking for a faulure return from
+.BR seteuid ().
 .SH ERRORS
 .\" .TP
 .\" .B EINVAL