jjs -J-Djava.ext.dirs=$jdk9_dev/nashorn/dist/ -doe

jjs> JSON.parse('{"0":0, "64":0}')

java.lang.ArrayIndexOutOfBoundsException: 64
java.lang.ArrayIndexOutOfBoundsException: 64
at jdk.nashorn.internal.runtime.arrays.IntArrayData.set(IntArrayData.java:215)
at jdk.nashorn.internal.runtime.arrays.IntArrayData.set(IntArrayData.java:204)
at jdk.nashorn.internal.runtime.arrays.ArrayFilter.set(ArrayFilter.java:102)
at jdk.nashorn.internal.runtime.arrays.DeletedRangeArrayFilter.set(DeletedRangeArrayFilter.java:132)
at jdk.nashorn.internal.runtime.ScriptObject.defineOwnProperty(ScriptObject.java:694)
at jdk.nashorn.internal.runtime.JSONFunctions.setPropertyValue(JSONFunctions.java:200)
at jdk.nashorn.internal.runtime.JSONFunctions.convertNode(JSONFunctions.java:182)
at jdk.nashorn.internal.runtime.JSONFunctions.parse(JSONFunctions.java:93)
at jdk.nashorn.internal.objects.NativeJSON.parse(NativeJSON.java:105)
at jdk.nashorn.internal.scripts.Script$Recompilation$3$\^shell\_.:program(<shell>:1)
at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:567)
at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:222)
at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:375)
at jdk.nashorn.internal.runtime.Context.eval(Context.java:633)
at jdk.nashorn.internal.runtime.Context.eval(Context.java:563)
at jdk.nashorn.tools.Shell.readEvalPrint(Shell.java:448)
at jdk.nashorn.tools.Shell.run(Shell.java:158)
at jdk.nashorn.tools.Shell.main(Shell.java:133)
at jdk.nashorn.tools.Shell.main(Shell.java:112)

The above works fine with jdk8 GA as well as jdk8u-dev tip build