why does this not work? runtime exception

Input.scala

import annotation.tailrec

object Input {
    def main(args: Array[String]) {
        println(askInput)
    }

    @tailrec
    private def askInput: String = {
        lazy val input = try readLine.toInt -1 catch {case _ => -1}
        if(input > 5)
            "Great!"
        else 
            askInput
    }
}

/*

"scalac Input.scala" works fine but then "scala Input" borks with this:
java.lang.VerifyError: (class: Input$, method: input$1 signature: (Lscala/runtime/IntRef;Lscala/runtime/VolatileIntRef;)I) Inconsistent stack height 0 != 1
        at Input.main(tailrec.scala)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at scala.tools.nsc.util.ScalaClassLoader$$anonfun$run$1.apply(ScalaClassLoader.scala:81)
        at scala.tools.nsc.util.ScalaClassLoader$class.asContext(ScalaClassLoader.scala:24)
        at scala.tools.nsc.util.ScalaClassLoader$URLClassLoader.asContext(ScalaClassLoader.scala:86)
        at scala.tools.nsc.util.ScalaClassLoader$class.run(ScalaClassLoader.scala:81)
        at scala.tools.nsc.util.ScalaClassLoader$URLClassLoader.run(ScalaClassLoader.scala:86)
        at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:83)
        at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)

*/