Cassandra 2.0.4 Unable To Initialize MemoryMeter

H,
I've upgraded cassandra from 1.2.13 to 2.0.4 on a cluster of 5 nodes. when i run nodetool -h localhost ring I see this errormessage in the end:
ERROR 10:33:28,324 Unable to initialize MemoryMeter (jamm not specified as javaagent). This means Cassandra will be unable to measure object sizes accurately and may consequently OOM.
according to this: https://issues.apache.org/jira/browse/CASSANDRA-6404, it should be fixed. I'm running java-1.7.0-oracle-1.7.0.45-1jpp.2.el6_4.x86_64.
This is the beginning of the process options: /usr/lib/jvm/java-1.7.0-oracle-1.7.0.45.x86_64/jre/bin/java -ea -javaagent:/usr/share/cassandra//lib/jamm-0.2.5.jar
Is there anyone who could point me in a direction where too look for a solution?
These error's, are they serious or mere cosmetic?
//john

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