diff --git a/shell-completion/bash/bootctl b/shell-completion/bash/bootctl
index 391fa67bfc1..e61188fee94 100644
--- a/shell-completion/bash/bootctl
+++ b/shell-completion/bash/bootctl
@@ -69,7 +69,7 @@ _bootctl() {
         fi
     done
 
-    if [[ -z $verb ]]; then
+    if [[ -z ${verb-} ]]; then
         comps=${VERBS[*]}
     elif __contains_word "$verb" ${VERBS[STANDALONE]}; then
         comps=''
diff --git a/shell-completion/bash/busctl b/shell-completion/bash/busctl
index 5a4acd337ff..1cc41d46187 100644
--- a/shell-completion/bash/busctl
+++ b/shell-completion/bash/busctl
@@ -140,7 +140,7 @@ _busctl() {
 
     n=$(($COMP_CWORD - $i))
 
-    if [[ -z $verb ]]; then
+    if [[ -z ${verb-} ]]; then
         comps=${VERBS[*]}
     elif __contains_word "$verb" ${VERBS[STANDALONE]}; then
         comps=''
diff --git a/shell-completion/bash/coredumpctl b/shell-completion/bash/coredumpctl
index 5fc11fdbd28..54b85725158 100644
--- a/shell-completion/bash/coredumpctl
+++ b/shell-completion/bash/coredumpctl
@@ -83,7 +83,7 @@ _coredumpctl() {
             fi
         done
 
-        if [[ -z $verb ]]; then
+        if [[ -z ${verb-} ]]; then
             comps=${VERBS[*]}
         elif __contains_word "$verb" ${VERBS[LIST]} ${VERBS[DUMP]}; then
             comps=''
diff --git a/shell-completion/bash/homectl b/shell-completion/bash/homectl
index fe909fbb411..f738bfb37f1 100644
--- a/shell-completion/bash/homectl
+++ b/shell-completion/bash/homectl
@@ -170,7 +170,7 @@ _homectl() {
         fi
     done
 
-    if [[ -z $verb ]]; then
+    if [[ -z ${verb-} ]]; then
         comps=${VERBS[*]}
     elif __contains_word "$verb" ${VERBS[NAME]}; then
         comps=$(__get_homes)
diff --git a/shell-completion/bash/hostnamectl b/shell-completion/bash/hostnamectl
index 0f69e23e6f8..6f1909b5994 100644
--- a/shell-completion/bash/hostnamectl
+++ b/shell-completion/bash/hostnamectl
@@ -77,7 +77,7 @@ _hostnamectl() {
         fi
     done
 
-    if [[ -z $verb ]]; then
+    if [[ -z ${verb-} ]]; then
         comps=${VERBS[*]}
     elif __contains_word "$verb" ${VERBS[CHASSIS]}; then
         comps='desktop laptop convertible server tablet handset watch embedded vm container'
diff --git a/shell-completion/bash/localectl b/shell-completion/bash/localectl
index fa0f8fdca1c..987ae34cc91 100644
--- a/shell-completion/bash/localectl
+++ b/shell-completion/bash/localectl
@@ -67,7 +67,7 @@ _localectl() {
         fi
     done
 
-    if [[ -z $verb ]]; then
+    if [[ -z ${verb-} ]]; then
         comps=${VERBS[*]}
     elif __contains_word "$verb" ${VERBS[VARIANTS]}; then
         comps=$(command localectl list-x11-keymap-layouts)
diff --git a/shell-completion/bash/loginctl b/shell-completion/bash/loginctl
index f94f191d89e..2d03fcca3ed 100644
--- a/shell-completion/bash/loginctl
+++ b/shell-completion/bash/loginctl
@@ -93,7 +93,7 @@ _loginctl () {
         fi
     done
 
-    if   [[ -z $verb ]]; then
+    if   [[ -z ${verb-} ]]; then
         comps="${VERBS[*]}"
 
     elif __contains_word "$verb" ${VERBS[SESSIONS]}; then
diff --git a/shell-completion/bash/machinectl b/shell-completion/bash/machinectl
index bc3a7889b38..0227167928a 100644
--- a/shell-completion/bash/machinectl
+++ b/shell-completion/bash/machinectl
@@ -95,7 +95,7 @@ _machinectl() {
         return 0
     fi
 
-    if [[ -z $verb ]]; then
+    if [[ -z ${verb-} ]]; then
         comps=${VERBS[*]}
 
     elif __contains_word "$verb" ${VERBS[STANDALONE]}; then
diff --git a/shell-completion/bash/networkctl b/shell-completion/bash/networkctl
index 1e4d0a2aaef..40ac13abf86 100644
--- a/shell-completion/bash/networkctl
+++ b/shell-completion/bash/networkctl
@@ -69,7 +69,7 @@ _networkctl() {
         return 0
     fi
 
-    if [[ -z $verb ]]; then
+    if [[ -z ${verb-} ]]; then
         comps=${VERBS[*]}
     elif __contains_word "$verb" ${VERBS[STANDALONE]}; then
         comps=''
diff --git a/shell-completion/bash/portablectl b/shell-completion/bash/portablectl
index e18d04c7ea8..a0ccc733adb 100644
--- a/shell-completion/bash/portablectl
+++ b/shell-completion/bash/portablectl
@@ -79,7 +79,7 @@ _portablectl() {
 
     n=$(($COMP_CWORD - $i))
 
-    if [[ -z $verb ]]; then
+    if [[ -z ${verb-} ]]; then
         comps=${VERBS[*]}
     elif __contains_word "$verb" ${VERBS[STANDALONE]}; then
         comps=''
diff --git a/shell-completion/bash/resolvectl b/shell-completion/bash/resolvectl
index dae4330d4c5..646a197a13f 100644
--- a/shell-completion/bash/resolvectl
+++ b/shell-completion/bash/resolvectl
@@ -87,7 +87,7 @@ _resolvectl() {
         fi
     done
 
-    if [[ -z $verb ]]; then
+    if [[ -z ${verb-} ]]; then
         comps="${VERBS[*]}"
 
     elif __contains_word "$verb" ${VERBS[STANDALONE]} ${VERBS[DOMAIN]}; then
diff --git a/shell-completion/bash/systemctl.in b/shell-completion/bash/systemctl.in
index e6e6ca0d7e0..b61f88b012c 100644
--- a/shell-completion/bash/systemctl.in
+++ b/shell-completion/bash/systemctl.in
@@ -254,7 +254,7 @@ _systemctl () {
         cur_orig="$(printf '%q' $cur)"
     fi
 
-    if [[ -z $verb ]]; then
+    if [[ -z ${verb-} ]]; then
         comps="${VERBS[*]}"
 
     elif __contains_word "$verb" ${VERBS[ALL_UNITS]}; then
diff --git a/shell-completion/bash/systemd-analyze b/shell-completion/bash/systemd-analyze
index eded49b50e7..36fcf432ff9 100644
--- a/shell-completion/bash/systemd-analyze
+++ b/shell-completion/bash/systemd-analyze
@@ -93,12 +93,12 @@ _systemd_analyze() {
         return 0
     fi
 
-    if [[ -z $verb  && $cur = -* ]]; then
+    if [[ -z ${verb-}  && $cur = -* ]]; then
         COMPREPLY=( $(compgen -W '${OPTS[*]}' -- "$cur") )
         return 0
     fi
 
-    if [[ -z $verb ]]; then
+    if [[ -z ${verb-} ]]; then
         comps=${VERBS[*]}
 
     elif __contains_word "$verb" ${VERBS[STANDALONE]}; then
diff --git a/shell-completion/bash/systemd-delta b/shell-completion/bash/systemd-delta
index 1a24dc07109..f94c1285332 100644
--- a/shell-completion/bash/systemd-delta
+++ b/shell-completion/bash/systemd-delta
@@ -53,7 +53,7 @@ _systemd-delta() {
         return 0
     fi
 
-    COMPREPLY=( $(compgen -W '$comps' -- "$cur") )
+    COMPREPLY=( $(compgen -W '${comps-}' -- "$cur") )
     return 0
 }
 
diff --git a/shell-completion/bash/systemd-id128 b/shell-completion/bash/systemd-id128
index 25110d13091..ad4731de18f 100644
--- a/shell-completion/bash/systemd-id128
+++ b/shell-completion/bash/systemd-id128
@@ -61,7 +61,7 @@ _systemd_id128() {
         fi
     done
 
-    if [[ -z $verb ]]; then
+    if [[ -z ${verb-} ]]; then
         comps=${VERBS[*]}
     elif __contains_word "$verb" ${VERBS[STANDALONE]}; then
         comps=''
diff --git a/shell-completion/bash/timedatectl b/shell-completion/bash/timedatectl
index 3e72ce6655e..29dc27b39cc 100644
--- a/shell-completion/bash/timedatectl
+++ b/shell-completion/bash/timedatectl
@@ -76,7 +76,7 @@ _timedatectl() {
         fi
     done
 
-    if [[ -z $verb ]]; then
+    if [[ -z ${verb-} ]]; then
         comps=${VERBS[*]}
     elif __contains_word "$verb" ${VERBS[BOOLEAN]}; then
         comps='true false'
diff --git a/shell-completion/bash/udevadm b/shell-completion/bash/udevadm
index d2c325b8686..81036f35883 100644
--- a/shell-completion/bash/udevadm
+++ b/shell-completion/bash/udevadm
@@ -73,7 +73,7 @@ _udevadm() {
         fi
     done
 
-    if [[ -z $verb ]]; then
+    if [[ -z ${verb-} ]]; then
         if [[ "$cur" = -* ]]; then
             COMPREPLY=( $(compgen -W '${OPTS[COMMON]} ${OPTS[DEBUG]}' -- "$cur") )
         else