Creating typeTag from String and pass it to a polymorphic Method

I have a polymorphic method that takes a custom case class as a type parameter. Now, in order to support several case classes (defined in a config file as a String), I need to convert a String to the tagType of the case class.

For that, I used runtimeMirror method to get the class from the String, and then I used manifestToTypeTag to get the tagType (Getting TypeTag from a classname string)

import scala.reflect.runtime.universe._
import scala.reflect.runtime.universe
import scala.reflect.ManifestFactory

// My polymorphic method
def printMe[T](l: List[T])(implicit typeTag: TypeTag[T]): Unit = println(l)

val className = "java.lang.String" // a Custom case class 
val mirror = universe.runtimeMirror(getClass.getClassLoader)
val cls = Class.forName(className)
// Getting the typeTag from the class name
val t = internal.manifestToTypeTag(mirror,ManifestFactory.classType(cls))

// Call of the method 
printMe(List("fdfg"))(t)

// Compilation error
Error:(12, 31) type mismatch;
found   : scala.reflect.api.Universe#TypeTag[Nothing]
required: reflect.runtime.universe.TypeTag[String]
Note: Nothing <: String, but trait TypeTag is invariant in type T.
You may wish to investigate a wildcard type such as `_ <: String`. (SLS 3.2.10)
printMe(List("fdfg"))(t)

However, when I pass the typeTag to my polymorphic method I get a "type match compilation error" shown above. Indeed, my polymorphic method requires a TypeTag[MyClassToto], and the TypeTag I generate is TypeTag[Nothing].

I wonder if is possible to cast the TypeTag I have got, or may be I have to change the signature of my polymorphic method ?