JsonSlurper LAX parser with invalid number

The JsonSlurper LAX parser parses an invalid number incorrectly:

import groovy.json.*

def obj = new JsonSlurper().setType(JsonParserType.LAX).parseText('{ "num": 1a}')
println "1a: num = ${obj.num}"
println "1a: type is " + obj.num.class.name

obj = new JsonSlurper().setType(JsonParserType.LAX).parseText('{ "num": 1A}')
println "1A: num = ${obj.num}"
println "1A: type is " + obj.num.class.name

produces:
1a: num = 59
1a: type is java.lang.Integer
1A: num = 27
1A: type is java.lang.Integer

It seems like the parser should fail this as an invalid number, though one could argue the LAX parser could interpret it as hex 1a, but neither is being done. Valid numbers are of course parsed correctly.