diff --git a/bash/rescue-hetzner.sh b/bash/rescue-hetzner.sh
index 81930b4..ee68157 100644
--- a/bash/rescue-hetzner.sh
+++ b/bash/rescue-hetzner.sh
@@ -16,7 +16,7 @@ rescue_wipe_0_init_hetzner_8_8() {
 	#
 	number=0
 	for device in "${devices[@]}"; do
-		((number++))
+		number=$((number + 1))
 		echo
 		echo "#${number}: ${device}"
 		#
@@ -33,7 +33,7 @@ rescue_wipe_0_init_hetzner_8_8() {
 	#
 	number=0
 	for device in "${devices[@]}"; do
-		((number++))
+		number=$((number + 1))
 		echo
 		echo "#${number}: ${device}4"
 		# wipe bios
@@ -42,7 +42,7 @@ rescue_wipe_0_init_hetzner_8_8() {
 	#
 	number=0
 	for device in "${devices[@]}"; do
-		((number++))
+		number=$((number + 1))
 		echo
 		echo "#${number}: ${device}3"
 		# format esp
@@ -55,7 +55,7 @@ rescue_wipe_0_init_hetzner_8_8() {
 	#
 	number=0
 	for device in "${devices[@]}"; do
-		((number++))
+		number=$((number + 1))
 		echo
 		echo "#${number}: ${device}2"
 		# wipe boot
@@ -85,7 +85,7 @@ rescue_wipe_0_init_hetzner_8_8() {
 	#
 	number=0
 	for device in "${devices[@]}"; do
-		((number++))
+		number=$((number + 1))
 		echo
 		echo "#${number}: ${device}1"
 		# wipe crypt head