diff --git a/include/wpml-config.php b/include/wpml-config.php
index 1aa2501..b33c266 100644
--- a/include/wpml-config.php
+++ b/include/wpml-config.php
@@ -248,7 +248,8 @@ public function copy_post_metas($metas, $sync) {
 				if ('copy' == $cf['attributes']['action'] || (!$sync && 'translate' == $cf['attributes']['action']))
 					$metas[] = $cf['value'];
 				else
-					$metas = array_diff($metas,  array($cf['value']));
+					if (isset($cf['value']))
+						$metas = array_diff($metas,  array($cf['value']));
 			}
 		}
 		return $metas;