diff --git a/htdocs/core/class/html.formmail.class.php b/htdocs/core/class/html.formmail.class.php
index 83d3af6d9db..ff6147977f3 100644
--- a/htdocs/core/class/html.formmail.class.php
+++ b/htdocs/core/class/html.formmail.class.php
@@ -831,7 +831,7 @@ class FormMail extends Form
 							$out .= '<input type="hidden" name="MAX_FILE_SIZE" value="'.($maxmin * 1024).'">';	// MAX_FILE_SIZE must precede the field type=file
 						}
 						// Can add other files
-						if (!empty($conf->global->FROM_MAIL_USE_INPUT_FILE_MULTIPLE)) {
+						if (empty($conf->global->FROM_MAIL_DONT_USE_INPUT_FILE_MULTIPLE)) {
 							$out .= '<input type="file" class="flat" id="addedfile" name="addedfile[]" value="'.$langs->trans("Upload").'" multiple />';
 						} else {
 							$out .= '<input type="file" class="flat" id="addedfile" name="addedfile" value="'.$langs->trans("Upload").'" />';