diff --git a/mongo/mongo-3/src/main/scala/io/sphere/mongo/format/MongoFormat.scala b/mongo/mongo-3/src/main/scala/io/sphere/mongo/format/MongoFormat.scala
index ffcf985..85b73db 100644
--- a/mongo/mongo-3/src/main/scala/io/sphere/mongo/format/MongoFormat.scala
+++ b/mongo/mongo-3/src/main/scala/io/sphere/mongo/format/MongoFormat.scala
@@ -59,10 +59,7 @@ object MongoFormat {
     inline private def deriveTrait[A](mirrorOfSum: Mirror.SumOf[A]): MongoFormat[A] =
       new MongoFormat[A] {
         private val traitMetaData = AnnotationReader.readTraitMetaData[A]
-        private val typeHintMap = traitMetaData.subtypes.collect {
-          case (name, classMeta) if classMeta.typeHint.isDefined =>
-            name -> classMeta.typeHint.get
-        }
+        private val typeHintMap = traitMetaData.subTypeTypeHints
         private val reverseTypeHintMap = typeHintMap.map((on, n) => (n, on))
         private val formatters = summonFormatters[mirrorOfSum.MirroredElemTypes]
         private val names = constValueTuple[mirrorOfSum.MirroredElemLabels].productIterator.toVector
diff --git a/mongo/mongo-3/src/main/scala/io/sphere/mongo/generic/AnnotationReader.scala b/mongo/mongo-3/src/main/scala/io/sphere/mongo/generic/AnnotationReader.scala
index 7b5c5a9..bcf32d8 100644
--- a/mongo/mongo-3/src/main/scala/io/sphere/mongo/generic/AnnotationReader.scala
+++ b/mongo/mongo-3/src/main/scala/io/sphere/mongo/generic/AnnotationReader.scala
@@ -28,6 +28,11 @@ case class TraitMetaData(
     subtypes: Map[String, CaseClassMetaData]
 ) {
   val typeDiscriminator: String = typeHintFieldRaw.map(_.value).getOrElse("type")
+
+  val subTypeTypeHints: Map[String, String] = subtypes.collect {
+    case (name, classMeta) if classMeta.typeHint.isDefined =>
+      name -> classMeta.typeHint.get
+  }
 }
 
 object AnnotationReader {