MVEL equality is not working as in 5.1.1

There is a different behavior caused by what I think is an MVEL regretion in the version that it's being used in 5.3.0.SNAPSHOT.

Patient( groupName == "ceftazidime susc islt" || groupName == "ceftfsdfsazidime susc islt") // this doesn't work

and

Patient( groupName == "ceftazidime susc islt") // This works!!

The field groupName is an Object that overrides the method equals following the java convention for comparing objects.

I'm attaching an isolated unit test showing this problem.