diff --git a/slick-additions-entity/src/main/scala/slick/additions/entity/Entity.scala b/slick-additions-entity/src/main/scala/slick/additions/entity/Entity.scala
index 8d8a99b..a3f01b6 100644
--- a/slick-additions-entity/src/main/scala/slick/additions/entity/Entity.scala
+++ b/slick-additions-entity/src/main/scala/slick/additions/entity/Entity.scala
@@ -1,20 +1,29 @@
 package slick.additions.entity
 
 
-sealed trait EntityRef[K, +A]
+sealed trait EntityRef[K, +A] {
+  def transform[B](f: A => B): EntityRef[K, B]
+  def widen[B >: A]: EntityRef[K, B]
+}
 
 sealed trait Lookup[K, +A] extends EntityRef[K, A] {
   def key: K
+  override def transform[B](f: A => B): Lookup[K, B]
+  override def widen[B >: A]: Lookup[K, B]
   def foldLookup[X](key: EntityKey[K, A] => X, ent: KeyedEntity[K, A] => X): X = this match {
     case ek: EntityKey[K, A]   => key(ek)
     case ke: KeyedEntity[K, A] => ent(ke)
   }
   def valueOption: Option[A] = foldLookup(_ => None, ke => Some(ke.value))
   def sameKey(that: Lookup[K, _]) = this.key == that.key
+  def toEntityKey: EntityKey[K, A]
 }
 
-case class EntityKey[K, +A](key: K) extends Lookup[K, A]
-
+case class EntityKey[K, +A](key: K) extends Lookup[K, A] {
+  override def transform[B](f: A => B): EntityKey[K, B] = copy()
+  override def widen[B >: A]: EntityKey[K, B] = transform(identity)
+  override def toEntityKey = this
+}
 
 sealed trait Entity[K, +A] extends EntityRef[K, A] {
   def keyOption: Option[K]
@@ -23,7 +32,8 @@ sealed trait Entity[K, +A] extends EntityRef[K, A] {
 
   def isSaved: Boolean
 
-  def transform[B](f: A => B): Entity[K, B]
+  override def transform[B](f: A => B): Entity[K, B]
+  override def widen[B >: A]: Entity[K, B]
   def modify[B](f: A => B): Entity[K, B]
 
   @deprecated("Use modify", "0.9.1")
@@ -44,6 +54,7 @@ case class KeylessEntity[K, +A](value: A) extends Entity[K, A] {
   override def equals(that: Any) = this eq that.asInstanceOf[AnyRef]
 
   override def transform[B](f: A => B): KeylessEntity[K, B] = new KeylessEntity[K, B](f(value))
+  override def widen[B >: A]: KeylessEntity[K, B] = transform(identity)
   override def modify[B](f: A => B) = transform(f)
   final override def map[B >: A](f: A => B): KeylessEntity[K, B] = modify(f)
 
@@ -54,11 +65,13 @@ sealed trait KeyedEntity[K, +A] extends Entity[K, A] with Lookup[K, A] {
   override def keyOption = Some(key)
 
   override def transform[B](f: A => B): KeyedEntity[K, B]
+  override def widen[B >: A]: KeyedEntity[K, B]
   override def modify[B](f: A => B): ModifiedEntity[K, B] = ModifiedEntity[K, B](key, f(value))
   final override def map[B >: A](f: A => B): ModifiedEntity[K, B] = modify(f)
 
   def toSaved: SavedEntity[K, A] = SavedEntity(key, value)
   def asLookup: Lookup[K, A] = this
+  override def toEntityKey = EntityKey(key)
 }
 object KeyedEntity {
   def apply[K, A](key: K, value: A): KeyedEntity[K, A] = SavedEntity[K, A](key, value)
@@ -66,9 +79,11 @@ object KeyedEntity {
 }
 case class SavedEntity[K, +A](key: K, value: A) extends KeyedEntity[K, A] {
   final override def isSaved = true
-  override def transform[B](f: A => B) = SavedEntity(key, f(value))
+  override def transform[B](f: A => B): SavedEntity[K, B] = SavedEntity(key, f(value))
+  override def widen[B >: A]: SavedEntity[K, B] = transform(identity)
 }
 case class ModifiedEntity[K, +A](key: K, value: A) extends KeyedEntity[K, A] {
   final override def isSaved = false
-  override def transform[B](f: A => B) = ModifiedEntity(key, f(value))
+  override def transform[B](f: A => B): ModifiedEntity[K, B] = ModifiedEntity(key, f(value))
+  override def widen[B >: A]: ModifiedEntity[K, B] = transform(identity)
 }