io.js error in cluster.worker with preload

gistfile1.txt

node -r './spm-agent-nodejs' cluster-test.js 
2015-03-27T21:22:28.475Z - info: config setting: ./spmlogs/spm.master.-STEFAN-.log
2015-03-27T21:22:28.486Z - info: {"_":[],"logger":{"dir":"./spmlogs","level":"debug","console":"true","maxfiles":"2","maxsize":"524288","filename":"spm","useLogstashFormat":false,"silent":false},"dbDir":"./spmdb","spmSenderBulkInsertUrl":"https://spm-receiver.sematext.com:443/receiver/v1/_bulk","maxRetransmitBatchSize":100,"transmitInterval":60000,"collectionInterval":30000,"recoverInterval":240000,"maxDataPoints":99,"agentsToLoad":[],"maxDbSize":25165824,"tokens":{"spm":"STEFAN"},"rcFlat":{"_":[],"logger.dir":"./spmlogs","logger.level":"debug","logger.console":"true","logger.maxfiles":"2","logger.maxsize":"524288","logger.filename":"spm","logger.useLogstashFormat":false,"logger.silent":false,"dbDir":"./spmdb","spmSenderBulkInsertUrl":"https://spm-receiver.sematext.com:443/receiver/v1/_bulk","maxRetransmitBatchSize":100,"transmitInterval":60000,"collectionInterval":30000,"recoverInterval":240000,"maxDataPoints":99,"agentsToLoad":[],"maxDbSize":25165824,"tokens.spm":"STEFAN"}}
2015-03-27T21:22:28.655Z - debug: SpmSender created for API endpoint: https://spm-receiver.sematext.com:443/receiver/v1/_bulk?agentType=nodejs&v=1.24.0&host=MacBook-Pro-2.local&token=STEFAN
/Users/stefan/node_modules/spm-agent-nodejs/node_modules/spm-agent/lib/util/logger.js:38
    postfix = '.worker-' + cluster.worker.id + '.-' + config.tokens.spm + '-.l
                                         ^
TypeError: Cannot read property 'id' of undefined
    at createLogger (/Users/stefan/node_modules/spm-agent-nodejs/node_modules/spm-agent/lib/util/logger.js:38:42)
    at Object.<anonymous> (/Users/stefan/node_modules/spm-agent-nodejs/node_modules/spm-agent/lib/util/logger.js:61:18)
    at Module._compile (module.js:410:26)
    at Object.Module._extensions..js (module.js:428:10)
    at Module.load (module.js:335:32)
    at Function.Module._load (module.js:290:12)
    at Module.require (module.js:345:17)
    at require (module.js:364:17)
    at Object.<anonymous> (/Users/stefan/node_modules/spm-agent-nodejs/node_modules/spm-agent/lib/agent.js:13:14)
    at Module._compile (module.js:410:26)