diff --git a/libexec/rc/rc.d/serial b/libexec/rc/rc.d/serial
--- a/libexec/rc/rc.d/serial
+++ b/libexec/rc/rc.d/serial
@@ -45,7 +45,7 @@
 	# Reset everything changed by the other functions to initial defaults.
 
 	dc=$1; shift	# device name character
-	drainwait=`sysctl -n kern.drainwait`
+	drainwait=`sysctl -n kern.tty_drainwait`
 
 	for i in $*
 	do
@@ -84,7 +84,7 @@
 	for i in $*
 	do
 		# may depend on modem
-		comcontrol /dev/tty${dc}${i} dtrwait 100 drainwait 180
+		comcontrol /dev/tty${dc}${i} drainwait 180
 		# Lock crtscts on.
 		# Speed reasonable for V42bis.
 		stty < /dev/tty${dc}${i}.init crtscts 115200