Getting ClassCast Exception when using seraph-paths.xml to secure additonal directories in confluence webapp

I added the following lines to the seraph-paths.xml and got the following ClasspathException when I tried to access the configured directories with a borwser.

<security-paths>
<path name="admin">
<url-pattern>/admin/*</url-pattern>
<role-name>_role_mapped_admin</role-name>
</path>

<path name="external">
<url-pattern>/resources/external/*</url-pattern>
<role-name>confluence_users</role-name>
</path>

<path name="internal">
<url-pattern>/resources/internal/*</url-pattern>
<role-name>confluence_administartors</role-name>
</path>
</security-paths>

Exception:
java.lang.ClassCastException: com.atlassian.user.impl.osuser.OSUUser
at com.atlassian.seraph.util.GroupCache.getGroups(GroupCache.java:33)
at com.atlassian.seraph.auth.GroupRoleMapper.hasRole(GroupRoleMapper.java:27)
at com.atlassian.confluence.security.ConfluenceRoleMapper.hasRole(ConfluenceRoleMapper.java:27)
at com.atlassian.seraph.filter.SecurityFilter.doFilter(SecurityFilter.java:151)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.atlassian.seraph.filter.LoginFilter.doFilter(LoginFilter.java:177)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at com.atlassian.core.filters.gzip.GzipFilter.doFilter(GzipFilter.java:61)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:868)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:663)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Unknown Source)