diff --git a/functions/product.php b/functions/product.php
index 73182896..3f37d46f 100644
--- a/functions/product.php
+++ b/functions/product.php
@@ -387,7 +387,7 @@ function doliProductCart($product, $refresh = null, $wishlist = true, $related =
   if ( empty(doliconnectid('dolicart')) || empty(doliconnectid('dolicart')) ) {
     $button .= "<a class='btn btn-block btn-info' href='".doliconnecturl('dolicontact')."?type=COM' role='button' title='".__( 'Contact us', 'doliconnect')."'>".__( 'Contact us', 'doliconnect').'</a>';
   } elseif ( is_user_logged_in() && doliCheckModules('commande', $refresh) && doliconnectid('dolicart') > 0 ) {
-    if (!empty($related) && $mstock['fk_parent_line']) {
+    if (!empty($related) && !empty($mstock['fk_parent_line'])) {
       $button .= '<input id="qty-prod-'.$product->id.'" type="text" class="form-control form-control-sm" value="'.__( 'Linked item', 'doliconnect').'" aria-label="'.__( 'Linked item', 'doliconnect').'" style="text-align:center;" disabled readonly>';
     } elseif ( $mstock['stock'] <= 0 || $mstock['m2'] < $mstock['step'] ) { 
       $button .= '<div class="input-group">';