Another type unsoundness of Scala

C.scala

class A {
  def compareTo(o: Any): Int = 0
}
class B extends A with Comparable[B] {
  def compareTo(b: B): Int = 0
}
object C {
  def main(args: Array[String]): Unit = {
    println(new B().compareTo(new Object()))
  }
}

console.txt

> scalac C.scala
> scala C
java.lang.ClassCastException: java.lang.Object cannot be cast to B
        at B.compareTo(C.scala:4)
        at C$.main(C.scala:9)
        at C.main(C.scala)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcces
        at java.lang.reflect.Method.invoke(Method.java:498)
        at scala.reflect.internal.util.ScalaClassLoader$$anonfun$run$1.apply(Sca
        at scala.reflect.internal.util.ScalaClassLoader$class.asContext(ScalaCla
        at scala.reflect.internal.util.ScalaClassLoader$URLClassLoader.asContext
        at scala.reflect.internal.util.ScalaClassLoader$class.run(ScalaClassLoad
        at scala.reflect.internal.util.ScalaClassLoader$URLClassLoader.run(Scala
        at scala.tools.nsc.CommonRunner$class.run(ObjectRunner.scala:22)
        at scala.tools.nsc.ObjectRunner$.run(ObjectRunner.scala:39)
        at scala.tools.nsc.CommonRunner$class.runAndCatch(ObjectRunner.scala:29)
        at scala.tools.nsc.ObjectRunner$.runAndCatch(ObjectRunner.scala:39)
        at scala.tools.nsc.MainGenericRunner.runTarget$1(MainGenericRunner.scala
        at scala.tools.nsc.MainGenericRunner.run$1(MainGenericRunner.scala:87)
        at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:98)
        at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:103)
        at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)