Strict warning: Only variables should be passed by reference in FeedsQueryPathParser->getMappingSources() (line 309...

I get the warning:

Strict warning: Only variables should be passed by reference in FeedsQueryPathParser->getMappingSources() (line 309...

repeatedly when setting up feeds. I found an easy fix though, simply change line 309 in FeedsQueryPathParser.inc:
$last_mapping = end(array_keys($mappings));
to

$akeys = array_keys($mappings);
$last_mapping = end($akeys);