diff --git a/scalding-core/src/main/scala/com/twitter/scalding/TypeDescriptor.scala b/scalding-core/src/main/scala/com/twitter/scalding/TypeDescriptor.scala
index 5ec10106af..6d09a18aca 100644
--- a/scalding-core/src/main/scala/com/twitter/scalding/TypeDescriptor.scala
+++ b/scalding-core/src/main/scala/com/twitter/scalding/TypeDescriptor.scala
@@ -28,7 +28,7 @@ import scala.language.experimental.{ macros => sMacros }
  * Note in the com.twitter.scalding.macros package there are macros to
  * generate this for case classes, which may be very convenient.
  */
-@implicitNotFound("This class is used to bind together a Fields instance to an instance of type T. There is a implicit macro that generates a TypeDescriptor[T] for any type T where T is Boolean, String, Short, Int, Long, FLoat, or Double, or an option of these, or a tuple or case class of a supported type. (Nested tuples and case classes are allowed.) If your type T is not one of these, then you must write your own TypeDescriptor.")
+@implicitNotFound("""This class is used to bind together a Fields instance to an instance of type T. There is a implicit macro that generates a TypeDescriptor[T] for any type T where T is Boolean, String, Short, Int, Long, FLoat, or Double, or an option of these (with the exception of Option[String]), or a tuple or case class of a supported type. (Nested tuples and case classes are allowed.) Note: Option[String] specifically is not allowed as Some("") and None are indistinguishable. If your type T is not one of these, then you must write your own TypeDescriptor.""")
 trait TypeDescriptor[T] extends java.io.Serializable {
   def setter: TupleSetter[T]
   def converter: TupleConverter[T]