Alfresco with Kerberos: Error creating bean with name globalAuthenticationFilter

I configured Alfresco 4.2.c to work with MIT Kerberos, following the documentation.
Because the documentation is only for Active Directory, I adapted some part to Kerberos by reading the forum.

Upon starting Alfresco, I get this error:

04:01:38,725 ERROR [org.alfresco.fileserver] CIFS server configuration error, Error creating bean with name 'globalAuthenticationFilter' defined in file [/home/alfresco/alfresco-community-4.2.c-installer-linux-x64/tomcat/webapps/alfresco/WEB-INF/classes/alfresco/subsystems/Authentication/kerberos/kerberos-filter-context.xml]: Invocation of init method failed; nested exception is java.lang.SecurityException: Configuration Error: No such file or directory

I haven't modified the kerberos-filter-context.xml.
Any idea what could trigger this message?
I can post any configuration file you want.
No debug info gets logged.