diff --git a/install.sh b/install.sh
index e2a637d43..ffa0479e0 100644
--- a/install.sh
+++ b/install.sh
@@ -679,7 +679,9 @@ ssl_cert_issue() {
     # get the port number for the standalone server
     local WebPort=80
     prompt_or_default WebPort "Please choose which port to use (default is 80): " "80" XUI_ACME_HTTP_PORT
-    if [[ ${WebPort} -gt 65535 || ${WebPort} -lt 1 ]]; then
+    if [[ -z ${WebPort} ]]; then
+        WebPort=80
+    elif [[ ! ${WebPort} =~ ^[1-9][0-9]*$ || ${WebPort} -gt 65535 ]]; then
         echo -e "${yellow}Your input ${WebPort} is invalid, will use default port 80.${plain}"
         WebPort=80
     fi
diff --git a/update.sh b/update.sh
index f3efb8a0a..40910eaa3 100755
--- a/update.sh
+++ b/update.sh
@@ -498,7 +498,9 @@ ssl_cert_issue() {
     # get the port number for the standalone server
     local WebPort=80
     read -rp "Please choose which port to use (default is 80): " WebPort
-    if [[ ${WebPort} -gt 65535 || ${WebPort} -lt 1 ]]; then
+    if [[ -z ${WebPort} ]]; then
+        WebPort=80
+    elif [[ ! ${WebPort} =~ ^[1-9][0-9]*$ || ${WebPort} -gt 65535 ]]; then
         echo -e "${yellow}Your input ${WebPort} is invalid, will use default port 80.${plain}"
         WebPort=80
     fi
diff --git a/x-ui.sh b/x-ui.sh
index 94e74198f..4125198c4 100644
--- a/x-ui.sh
+++ b/x-ui.sh
@@ -1838,7 +1838,9 @@ ssl_cert_issue() {
     # get the port number for the standalone server
     local WebPort=80
     read -rp "Please choose which port to use (default is 80): " WebPort
-    if [[ ${WebPort} -gt 65535 || ${WebPort} -lt 1 ]]; then
+    if [[ -z ${WebPort} ]]; then
+        WebPort=80
+    elif [[ ! ${WebPort} =~ ^[1-9][0-9]*$ || ${WebPort} -gt 65535 ]]; then
         LOGE "Your input ${WebPort} is invalid, will use default port 80."
         WebPort=80
     fi