What does this.type refer to in a trait?

I thought that inside a trait, this referred to the object with the trait. But judging from the code below, sometimes it does and sometimes it doesn't.

import scala.reflect.runtime.universe._

trait Trait {
  val ttag = typeOf[this.type]
  println(s"Trait constructor: $this")
}

object Instance1 extends Trait

object Instance2 extends Trait

println(typeOf[Instance1.type] =:= typeOf[Instance2.type])  // Should be false
println(Instance1.ttag =:= Instance2.ttag)                  // Should be false

Here's the output:

Trait constructor: $line9.$read$$iw$$iw$$iw$$iw$Instance1$@58c46295
Trait constructor: $line10.$read$$iw$$iw$$iw$$iw$Instance2$@452451ba
false    // As expected: the singleton types of two objects are different
true     // But the this.type tags are equivalent!

So, there are two distinct objects, but apparently each is getting an equivalent type tag for its this.type.

Is this a compiler bug, or, if not, could you explain why this behavior makes sense?

(I'm running Scala 2.11.2. I've tried it with a self alias for this, with the same result.)