diff --git a/packages/effect-fc/src/Lens.ts b/packages/effect-fc/src/Lens.ts
index 18d10b3..6c7da97 100644
--- a/packages/effect-fc/src/Lens.ts
+++ b/packages/effect-fc/src/Lens.ts
@@ -74,21 +74,21 @@ export const fromSubscriptionRef = <A>(
 export const map = <A, ER, RR, EW, RW, B>(
     self: Lens<A, ER, RR, EW, RW>,
     get: (a: A) => B,
-    set: (b: B, parent: A) => A,
+    set: {
+        (parent: A, b: B): A
+        (b: B): (parent: A) => A
+    },
 ): Lens<B, ER, RR, EW, RW> => {
-    const getEffect = Effect.map(self.get, get)
-    const changes = Stream.map(self.changes, get)
-    const modify = <C, E1 = never, R1 = never>(
-        h: (b: B) => Effect.Effect<readonly [C, B], E1, R1>
-    ) => self.modify((a: A) => {
-        const b = get(a)
-        return Effect.flatMap(h(b), ([c, bNext]) => Effect.succeed([c, set(bNext, a)] as const))
-    })
+    const setF =
 
     return make({
-        get: getEffect,
-        changes,
-        modify,
+        get: Effect.map(self.get, get),
+        changes: Stream.map(self.changes, get),
+        modify: <C, E1 = never, R1 = never>(
+            f: (b: B) => Effect.Effect<readonly [C, B], E1, R1>
+        ) => self.modify((a: A) =>
+            Effect.flatMap(f(get(a)), ([c, next]) => Effect.succeed([c, set(a, next)] as const))
+        ),
     })
 }
 
@@ -104,8 +104,8 @@ export const mapEffect = <A, ER, RR, EW, RW, B, EGet = never, RGet = never, ESet
     ) => self.modify((a: A) => Effect.flatMap(getF(a), b => Effect.flatMap(h(b), ([c, bNext]) => Effect.flatMap(setF(bNext, a), nextA => Effect.succeed([c, nextA] as const)))))
 
     return make({
-        get,
-        changes,
+        get: Effect.flatMap(self.get, getF),
+        changes: Stream.mapEffect(self.changes, getF),
         modify,
     })
 }