diff --git a/etc/rc b/etc/rc
index 576ddf937af..278c9de494c 100644
--- a/etc/rc
+++ b/etc/rc
@@ -135,16 +135,16 @@ done
 # Note: this assumes firstboot_sentinel is on / when we have
 # a read-only /, or that it is on media that's writable.
 if [ -e ${firstboot_sentinel} ]; then
-	[ ${root_rw_mount} = "yes" ] || mount -uw /
+	[ ${root_rw_mount#[Yy][Ee][Ss]} = "" ] || mount -uw /
 	chflags -R 0 ${firstboot_sentinel}
 	rm -rf ${firstboot_sentinel}
 	if [ -e ${firstboot_sentinel}-reboot ]; then
 		chflags -R 0 ${firstboot_sentinel}-reboot
 		rm -rf ${firstboot_sentinel}-reboot
-		[ ${root_rw_mount} = "yes" ] || mount -ur /
+		[ ${root_rw_mount#[Yy][Ee][Ss]} = "" ] || mount -ur /
 		kill -INT 1
 	fi
-	[ ${root_rw_mount} = "yes" ] || mount -ur /
+	[ ${root_rw_mount#[Yy][Ee][Ss]} = "" ] || mount -ur /
 fi
 
 echo ''