diff --git a/src/etc/inc/util.inc b/src/etc/inc/util.inc
index 3cf06152f..bc918e13b 100644
--- a/src/etc/inc/util.inc
+++ b/src/etc/inc/util.inc
@@ -744,16 +744,17 @@ function is_hostname($hostname)
 }
 
 /* returns true if $domain is a valid domain name */
-function is_domain($domain)
+function is_domain($domain, $allow_root = false)
 {
     if (!is_string($domain)) {
         return false;
-    }
-    if (preg_match('/^(?:(?:[a-z0-9]|[a-z0-9][a-z0-9\-]*[a-z0-9])\.)*(?:[a-z0-9]|[a-z0-9][a-z0-9\-]*[a-z0-9])$/i', $domain)) {
+    } elseif (preg_match('/^(?:(?:[a-z0-9]|[a-z0-9][a-z0-9\-]*[a-z0-9])\.)*(?:[a-z0-9]|[a-z0-9][a-z0-9\-]*[a-z0-9])$/i', $domain)) {
+        return true;
+    } elseif ($allow_root && $domain == '.') {
         return true;
-    } else {
-        return false;
     }
+
+    return false;
 }
 
 /* returns true if $macaddr is a valid MAC address */
diff --git a/src/www/services_router_advertisements.php b/src/www/services_router_advertisements.php
index d19bfcc3c..7faca9773 100644
--- a/src/www/services_router_advertisements.php
+++ b/src/www/services_router_advertisements.php
@@ -118,7 +118,7 @@ if ($_SERVER['REQUEST_METHOD'] === 'GET') {
     if (!empty($pconfig['radomainsearchlist'])) {
         $domain_array=preg_split("/[ ;]+/",$pconfig['radomainsearchlist']);
         foreach ($domain_array as $curdomain) {
-            if (!is_domain($curdomain)) {
+            if (!is_domain($curdomain, true)) {
                 $input_errors[] = gettext("A valid domain search list must be specified.");
                 break;
             }