BPEL validator does not recognize counter variable inside forEach.

The declared counter variable in the following code snippet is marked by the validator red (see attached image).

CODE

...
<bpel:variable name="number" type="xsd:int"/>
...
<bpel:forEach parallel="no" counterName="counter" name="ForEach">
<bpel:startCounterValue><![CDATA[1]]></bpel:startCounterValue>
<bpel:finalCounterValue><![CDATA[10]]></bpel:finalCounterValue>
<bpel:scope name="Scope">
<bpel:assign validate="no" name="Assign">
<bpel:copy>
<bpel:from variable="counter"/>
<bpel:to variable="number"/>
</bpel:copy>
</bpel:assign>
</bpel:scope>
</bpel:forEach>