Cannot set array variable using script task

When I try to set an array type variable in a javascript script task:

<![CDATA[
var assigneeList = ["kermit", "gonzo", "fozzie"];
execution.setVariable("assigneeList", assigneeList);
print("List: " + assigneeList);
]]>

I get a serialization error:

10:55:27,153 [main] ERROR org.flowable.engine.impl.test.AbstractTestCase - EXCEPTION: org.flowable.engine.common.api.FlowableException: problem evaluating script: sun.org.mozilla.javascript.internal.WrappedException: Wrapped org.flowable.engine.common.api.FlowableException: couldn’t find a variable type that is able to serialize sun.org.mozilla.javascript.internal.NativeArray@d6401d3 (#3) in at line number 3
org.flowable.engine.common.api.FlowableException: problem evaluating script: sun.org.mozilla.javascript.internal.WrappedException: Wrapped org.flowable.engine.common.api.FlowableException: couldn’t find a variable type that is able to serialize sun.org.mozilla.javascript.internal.NativeArray@d6401d3 (#3) in at line number 3
...

Reference discussion: https://forum.flowable.org/t/multi-instance-collection-syntax-proposal/615/13