GetFeatureInfo returns non valid GML document with clustered layer

[dr]

Try to use GetFeatureInfo with clustered layer. Example of WMS server response:

<?xml version="1.0" encoding="ISO-8859-1"?>

<msGMLOutput 
	 xmlns:gml="http://www.opengis.net/gml"
	 xmlns:xlink="http://www.w3.org/1999/xlink"
	 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
	<herbary_layer>
		<herbary_feature>
			<gml:boundedBy>
				<gml:Box srsName="EPSG:900913">
					<gml:coordinates>11687998.450672,11932751.091976 11687998.450672,11932751.091976</gml:coordinates>
				</gml:Box>
			</gml:boundedBy>
			<Cluster:FeatureCount>1</Cluster:FeatureCount>
			<Cluster:Group></Cluster:Group>
		</herbary_feature>
	</herbary_layer>
</msGMLOutput>

But this document is not valid. Try to parse it within OpenLayers I get an error message: "XML Parsing Error: prefix not bound to a namespace". Is it possible to exclude <Cluster:FeatureCount> and <Cluster:Group> tags from server response?