Index: usr.sbin/freebsd-update/freebsd-update.sh
===================================================================
--- usr.sbin/freebsd-update/freebsd-update.sh
+++ usr.sbin/freebsd-update/freebsd-update.sh
@@ -580,6 +580,7 @@
 	_KEYPRINT_z="Key must be given via -k option or configuration file."
 	_KEYPRINT_bad="Invalid key fingerprint: "
 	_WORKDIR_bad="Directory does not exist or is not writable: "
+	_WORKDIR_bad2="Directory is not on a persistent filesystem: "
 
 	if [ -z "${SERVERNAME}" ]; then
 		echo -n "`basename $0`: "
@@ -603,6 +604,14 @@
 		echo ${WORKDIR}
 		exit 1
 	fi
+	for i in tmpfs mdmfs; do
+		if df -t ${i} ${WORKDIR} >/dev/null 2>1; then
+			echo -n "`basename $0`: "
+			echo -n "${_WORKDIR_bad2}"
+			echo ${WORKDIR}
+			exit 1
+		fi
+	done
 	chmod 700 ${WORKDIR}
 	cd ${WORKDIR} || exit 1