Index: trunk/tools/checkstyle/josm_checks.xml
===================================================================
--- trunk/tools/checkstyle/josm_checks.xml	(revision 10414)
+++ trunk/tools/checkstyle/josm_checks.xml	(revision 10415)
@@ -115,4 +115,5 @@
   <module name="SuppressionFilter">
     <property name="file" value="${basedir}/tools/checkstyle/josm_filters.xml" default="tools/checkstyle/josm_filters.xml"/>
+    <property name="optional" value="true"/>
   </module>
 </module>