diff --git a/prototype/Doubt/Prism.swift b/prototype/Doubt/Prism.swift
index 642fab688..bfb445e71 100644
--- a/prototype/Doubt/Prism.swift
+++ b/prototype/Doubt/Prism.swift
@@ -28,24 +28,10 @@ extension Prism where To : ArrayConvertible {
 			},
 			backward: { To(array: [ $0 ]) })
 	}
-}
 
-
-public struct Iso<Here, There> {
-	public init(forward: Here -> There, backward: There -> Here) {
-		self.forward = forward
-		self.backward = backward
-	}
-
-	public let forward: Here -> There
-	public let backward: There -> Here
-}
-
-
-extension Prism where To : ArrayConvertible {
-	public func map<A>(transform: Iso<To.Element, A>) -> Prism<From, [A]> {
+	public func map<A>(transform: Prism<To.Element, A>) -> Prism<From, [A]> {
 		return Prism<From, [A]>(
-			forward: { self.forward($0)?.array.map(transform.forward) },
+			forward: { self.forward($0)?.array.flatMap(transform.forward) },
 			backward: { self.backward(To(array: $0.map(transform.backward))) })
 	}
 }