diff --git a/lib/org/openpsa/invoices/invoice/pdf.php b/lib/org/openpsa/invoices/invoice/pdf.php
index cee033e41..c74b1f053 100644
--- a/lib/org/openpsa/invoices/invoice/pdf.php
+++ b/lib/org/openpsa/invoices/invoice/pdf.php
@@ -40,7 +40,7 @@ public function get_attachment(bool $autocreate = false, string $kind = null) :
     public function get_button_options(string $kind = 'invoice') : array
     {
         if ($attachment = $this->get_attachment()) {
-            if ($this->invoice->sent && (!($kind == 'reminder'))) {
+            if ($this->invoice->sent && !($kind == 'reminder')) {
                 $message = 'invoice has already been sent. should it be replaced?';
             }
             // check if auto generated parameter is same as md5 in current-file