Call-time pass-by-reference has been deprecated

Every time cron runs, I get an email with the following message (php 5.2.9):

<br />
<b>Warning</b>:  Call-time pass-by-reference has been deprecated in <b>sites/all/modules/mailhandler/mailhandler.retrieve.inc</b> on line <b>264</b><br />

Line 264 reads: node_object_prepare(&$node);

Removing the "&" from the parameter removes the warning.