diff --git a/htdocs/core/class/html.form.class.php b/htdocs/core/class/html.form.class.php
index 7d2851f1b31..8f35a486dbe 100644
--- a/htdocs/core/class/html.form.class.php
+++ b/htdocs/core/class/html.form.class.php
@@ -3755,7 +3755,7 @@ class Form
         	if ($defaulttx < 0 || dol_strlen($defaulttx) == 0)
         	{
         		if (empty($conf->global->MAIN_VAT_DEFAULT_IF_AUTODETECT_FAILS)) $defaulttx = $this->cache_vatrates[$num-1]['txtva'];
-        		else $defaulttx=$conf->global->MAIN_VAT_DEFAULT_IF_AUTODETECT_FAILS;
+        		else $defaulttx=($conf->global->MAIN_VAT_DEFAULT_IF_AUTODETECT_FAILS == 'none' ? '' : $conf->global->MAIN_VAT_DEFAULT_IF_AUTODETECT_FAILS);
         	}
 
         	// Disabled if seller is not subject to VAT