diff --git a/controllers/admin/AdminLiteSpeedCacheCustomizeController.php b/controllers/admin/AdminLiteSpeedCacheCustomizeController.php
index ef36ccd..359113c 100644
--- a/controllers/admin/AdminLiteSpeedCacheCustomizeController.php
+++ b/controllers/admin/AdminLiteSpeedCacheCustomizeController.php
@@ -353,10 +353,8 @@ private function validateInput($name)
                     $postVal = '';
                 } else {
                     foreach ($clean as $ci) {
-                        if (!preg_match('/^(\!)?([a-zA-Z_]+)$/', $ci, $m)) {
+                        if (!preg_match('/^(\!)?([a-zA-Z_0-9]+)$/', $ci, $m)) {
                             $this->errors[] = $invalid . $s . $invalidChars;
-                        } else {
-                            // no further validation for now
                         }
                     }
                     $postVal = implode(', ', $clean);