Scala Reflection: Invoking a Function1's apply method - multiple alternatives?

I'm trying to invoke a function using the scala reflection api in v2.11.6:

import scala.reflect.runtime.{universe => ru}

def f(i: Int) = i + 2

val fn: Any = (f _)
val ref = ru.runtimeMirror(ru.getClass.getClassLoader).reflect(fn)
val apply = ref.symbol.typeSignature.member(ru.TermName("apply"))

When using ref.reflectMethod(apply.asMethod) it complains about multiple alternatives to apply on ref. Examining apply.asTerm.alternatives reveals two methods, one with signature (x$1: Int)Int and the other with (v1: T1)R. Calling

ref.reflectMethod(apply.asTerm.alternatives(1).asInstanceOf[ru.MethodSymbol])(1)

(with the second alternative) returns the correct result (3). However calling the first alternative raises an exception: java.lang.IllegalArgumentException: object is not an instance of declaring class

What are those alternatives and how can I make sure to always invoke the proper one?