=== modified file 'bin/confz'
--- bin/confz	2014-06-26 18:23:05 +0000
+++ bin/confz	2014-06-26 18:08:30 +0000
@@ -50,7 +50,7 @@
 
 # set $vars parameter if it's empty (ie. set default value)
 defvar() {
-	if ! (($+vars[$1])); then
+	if ! (($+vars[$1])) || [[ -z $vars[$1] ]]; then
 		setvar $1 $2
 	fi
 }
@@ -60,7 +60,7 @@
 	local var
 	local -a empty
 	for var in "$@"; do
-		if ! (($+vars[$var])); then
+		if ! (($+vars[$var])) || [[ -z $vars[$var] ]]; then
 			empty+=( $var )
 		fi
 	done

=== modified file 'zsh-functions/confz_fs_init'
--- zsh-functions/confz_fs_init	2014-06-26 18:23:05 +0000
+++ zsh-functions/confz_fs_init	2014-06-25 09:05:17 +0000
@@ -7,10 +7,12 @@
 
 # configure LVM2 logical volume
 confz_logical_volume_check() {
-	[[ -n ${vars[vg_name]:=${DEFAULT_VG}} ]] || \
+	defvar vg_name ${DEFAULT_VG:-}
+	[[ -n ${vars[vg_name]} ]] || \
 		die "$0: DEFAULT_VG is unset and no 'vg_name' was passed"
 
-	[[ -n ${vars[size]:=${DEFAULT_VOLUME_SIZE}} ]] || \
+	defvar size ${DEFAULT_VOLUME_SIZE:-}
+	[[ -n ${vars[size]} ]] || \
 		die "$0: DEFAULT_VOLUME_SIZE is unset and no 'size' was passed"
 
 	checkvars lv_name
@@ -31,7 +33,8 @@
 
 # create filesystem on block device
 confz_filesystem_check() {
-	[[ -n ${vars[filesystem]:=${DEFAULT_FS}} ]] || \
+	defvar filesystem ${DEFAULT_FS:-}
+	[[ -n ${vars[filesystem]} ]] || \
 		die "$0: DEFAULT_FS is unset and no 'filesystem' was passed"
 
 	checkvars label device filesystem

=== modified file 'zsh-functions/confz_vserver_init'
--- zsh-functions/confz_vserver_init	2014-06-26 18:23:05 +0000
+++ zsh-functions/confz_vserver_init	2014-06-26 18:15:23 +0000
@@ -78,7 +78,7 @@
 	vserver --silent -- $vars[name] running || return $?
 	local context_id
 	context_id=$(</etc/vservers/$vars[name]/run)
-	if ! (($+vars[context_id])); then
+	if [[ -z $vars[context_id] ]]; then
 		vars[context_id]=$context_id
 	elif (( $vars[context_id] != $context_id )); then
 		die "vserver ${(qqq)name} running under context id $context_id, expected $vars[context_id]"