diff --git a/htdocs/core/antispamimage.php b/htdocs/core/antispamimage.php
index c3bc217e100..a16844dd715 100644
--- a/htdocs/core/antispamimage.php
+++ b/htdocs/core/antispamimage.php
@@ -51,8 +51,6 @@ for($i = 0; $i < $length; $i++)
 $sessionkey='dol_antispam_value';
 $_SESSION[$sessionkey]=$string;
 
-header("Content-type: image/png");
-
 $img = imagecreate(80,32);
 if (empty($img))
 {
@@ -60,6 +58,8 @@ if (empty($img))
     exit;
 }
 
+header("Content-type: image/png");
+
 $background_color = imagecolorallocate($img, 250, 250, 250);
 $ecriture_color = imagecolorallocate($img, 0, 0, 0);
 imagestring($img, 4, 24, 8, $string, $ecriture_color);