diff --git a/src/Security/PermissionCheckboxSetField.php b/src/Security/PermissionCheckboxSetField.php
index fde5ad178..51fa3ff06 100644
--- a/src/Security/PermissionCheckboxSetField.php
+++ b/src/Security/PermissionCheckboxSetField.php
@@ -207,7 +207,7 @@ class PermissionCheckboxSetField extends FormField
 
                     $odd = ($odd + 1) % 2;
                     $extraClass = $odd ? 'odd' : 'even';
-                    $extraClass .= ' val' . str_replace(' ', '', $code ?? '');
+                    $extraClass .= ' val' . str_replace([' ', '\\'], ['', '-'], $code ?? '');
                     $itemID = $this->ID() . '_' . preg_replace('/[^a-zA-Z0-9]+/', '', $code ?? '');
                     $disabled = $inheritMessage = '';
                     $checked = (isset($uninheritedCodes[$code]) || isset($inheritedCodes[$code]))