diff --git a/core-lib/shared/src/main/scala/special/collection/package.scala b/core-lib/shared/src/main/scala/special/collection/package.scala
index 826c1bd3b5..b8be71be23 100644
--- a/core-lib/shared/src/main/scala/special/collection/package.scala
+++ b/core-lib/shared/src/main/scala/special/collection/package.scala
@@ -20,5 +20,14 @@ package object collection {
   /** Implicit resolution of `Coll[A]` type descriptor, given a descriptor of `A`. */
   implicit def collRType[A](implicit tA: RType[A]): RType[Coll[A]] = CollType[A](tA)
 
+  /** Conversion to underlying descriptor class.
+    * Allows syntax like
+    *
+    * ```val tColl: RType[Coll[A]] = ...; tColl.tItem```
+    *
+    * where `tItem` is a method of `CollType`, but is not defined on `RType`.
+    */
+  implicit def downcastCollType[A](ct: RType[Coll[A]]): CollType[A] = ct.asInstanceOf[CollType[A]]
+
   implicit val collBuilderRType: RType[CollBuilder] = RType.fromClassTag(classTag[CollBuilder])
 }