diff --git a/htdocs/contact/class/contact.class.php b/htdocs/contact/class/contact.class.php
index ab6e3c732c9..9cb5f4a7867 100644
--- a/htdocs/contact/class/contact.class.php
+++ b/htdocs/contact/class/contact.class.php
@@ -354,7 +354,7 @@ class Contact extends CommonObject
 		$this->lastname = $this->lastname ?trim($this->lastname) : trim($this->name);
         $this->firstname = trim($this->firstname);
         if (!empty($conf->global->MAIN_FIRST_TO_UPPER)) $this->lastname = ucwords(strtolower($this->lastname));
-		if (!empty($conf->global->MAIN_ALL_TO_UPPER)) $this->lastname = strtoupper($this->lastname);
+		if (!empty($conf->global->MAIN_ALL_TO_UPPER)) $this->lastname = dol_strtoupper($this->lastname);
         if (!empty($conf->global->MAIN_FIRST_TO_UPPER)) $this->firstname = ucwords(strtolower($this->firstname));
         if (empty($this->socid)) $this->socid = 0;
 		if (empty($this->priv)) $this->priv = 0;
@@ -465,7 +465,7 @@ class Contact extends CommonObject
 
 		// Clean parameters
 		if (!empty($conf->global->MAIN_FIRST_TO_UPPER)) $this->lastname = ucwords(strtolower($this->lastname));
-		if (!empty($conf->global->MAIN_ALL_TO_UPPER)) $this->lastname = strtoupper($this->lastname);
+		if (!empty($conf->global->MAIN_ALL_TO_UPPER)) $this->lastname = dol_strtoupper($this->lastname);
         if (!empty($conf->global->MAIN_FIRST_TO_UPPER)) $this->firstname = ucwords(strtolower($this->firstname));
 
 		$this->lastname = trim($this->lastname) ?trim($this->lastname) : trim($this->lastname);