How to exclude class name to phpmd, cleancode ruelset?

When I run phpmd I get this error (from cleancode ruleset): Avoid using static access to class '\Namespace\Domain\Exception\UserExceptions'

I make a phpmd.xml with this content:

<?xml version="1.0"?>
<ruleset>
   <rule ref="rulesets/cleancode.xml">
       <properties>
           <property name="exceptions" value="'\Namespace\Domain\Exception\UserExceptions' "/>
       </properties>
   </rule>
</ruleset> 

But this not working for me, Is my syntax wrong to specify the class name?