diff --git a/packages/effect-lens/src/Lens.ts b/packages/effect-lens/src/Lens.ts
index 82eabc0..57b23d5 100644
--- a/packages/effect-lens/src/Lens.ts
+++ b/packages/effect-lens/src/Lens.ts
@@ -31,11 +31,22 @@ export const isLens = (u: unknown): u is Lens<unknown, unknown, unknown, unknown
 export const LensStepTypeId: unique symbol = Symbol.for("@effect-fc/Lens/LensStep")
 export type LensStepTypeId = typeof LensTypeId
 
-export interface LensStep<in out A, in out B, in out ER = never, in out EW = never, in out RR = never, in out RW = never> {
+export interface LensStep<
+    in out A,
+    in out B,
+    in out ER = never,
+    in out EW = never,
+    in out RR = never,
+    in out RW = never,
+    in out SourceER = never,
+    in out SourceEW = never,
+    in out SourceRR = never,
+    in out SourceRW = never,
+> {
     readonly [LensStepTypeId]: LensStepTypeId
-    readonly transform: (parent: B) => Effect.Effect<A, ER, RR>
-    readonly transformStream: (parent: B) => Stream.Stream<A, ER, RR>
-    readonly update: (next: A, parent: B) => Effect.Effect<B, EW, RW>
+    readonly transform: (effect: Effect.Effect<B, SourceER, SourceRR>) => Effect.Effect<A, ER, RR>
+    readonly transformStream: (stream: Stream.Stream<B, SourceER, SourceRR>) => Stream.Stream<A, ER, RR>
+    readonly update: (next: Effect.Effect<A, SourceEW, SourceRW>, parent: B) => Effect.Effect<B, EW, RW>
 }
 
 export const isLensStep = (u: unknown): u is LensStep<unknown, unknown, unknown, unknown, unknown, unknown> => Predicate.hasProperty(u, LensStepTypeId)
@@ -71,7 +82,7 @@ extends Pipeable.Class() implements Lens<A, ER, EW, RR, RW> {
     readonly [LensTypeId]: LensTypeId = LensTypeId
     readonly [LensImplTypeId]: LensImplTypeId = LensImplTypeId
 
-    readonly steps: readonly LensStep<B, SER, SEW, SRR, SRW>[] = []
+    readonly steps: readonly LensStep<A, B, ER, EW, RR, RW, SourceER, SourceEW, SourceRR, SourceRW>[] = []
 
     abstract readonly sourceGet: Effect.Effect<B, SourceER, SourceRR>
     abstract readonly sourceChanges: Stream.Stream<B, SourceER, SourceRR>