=== modified file 'zsh-functions/confz_fs_init'
--- zsh-functions/confz_fs_init	2015-04-20 12:39:30 +0000
+++ zsh-functions/confz_fs_init	2015-04-20 12:26:58 +0000
@@ -73,15 +73,13 @@
 	fs_parted_list $vars[device]
 	(( $+vars[size] || $+vars[end] )) || die "$0: requires either size or end"
 	if [[ $vars[number] != 1 ]]; then
-		local prev
-		prev=$[ $vars[number] - 1 ]
-		(( $+fs_parted_start[$prev] )) || die "$0: missing preceding partition"
-		: ${vars[start]:=${fs_parted_start[$prev]}}
-	else
-		checkvars start
+		(( $+fs_parted_start[$vars[number]-1] )) || \
+			die "$0: missing preceding partition"
 	fi
+	[[ -n ${vars[start]:=${fs_parted_start[$vars[number]-1]:-}} ]] || \
+		die "$0: start not specified and no preceding partition"
 	if ! (($+vars[end])); then
-		vars[end]=$[${${vars[start]}%s} + ${${vars[size]}%s}]
+		vars[end]=$[$vars[start]+$vars[size]]
 	fi
 	if (( $+fs_parted_start[$vars[number]] )); then
 		return 0