diff --git a/packages/effect-lens/src/Lens.ts b/packages/effect-lens/src/Lens.ts
index 5210b17..a5d1082 100644
--- a/packages/effect-lens/src/Lens.ts
+++ b/packages/effect-lens/src/Lens.ts
@@ -79,7 +79,7 @@ export const asLensImpl = <A, ER, EW, RR, RW>(
     lens: Lens<A, ER, EW, RR, RW>
 ): LensImpl<A, ER, EW, RR, RW> => {
     if (!isLensImpl(lens))
-        throw new Error("Not a 'LensImpl'.")
+        throw new Error("Not a 'LensImpl'")
     return lens as LensImpl<A, ER, EW, RR, RW>
 }
 
@@ -122,67 +122,6 @@ export const make = <A, ER, EW, RR, RW>(
 ): Lens<A, ER, EW, RR, RW> => new LensLazyImpl(source)
 
 
-export declare namespace DerivedLensImpl {
-    export interface Source<
-        in out A,
-        in out B,
-        in out ER = never,
-        in out ESR = never,
-        in out EW = never,
-        in out ESW = never,
-        in out RR = never,
-        in out RSR = never,
-        in out RW = never,
-        in out RSW = never,
-    > {
-        readonly resolve: (effect: Effect.Effect<LensImpl.Resolved<B, ESW, RSW>, ESR, RSR>) => Effect.Effect<LensImpl.Resolved<A, EW, RW>, ER, RR>
-        readonly mapStream: (stream: Stream.Stream<B, ESR, RSR>) => Stream.Stream<A, ER, RR>
-        readonly mapLock: (lock: Effect.Effect<LensImpl.Lock, ESW, RSW>) => Effect.Effect<LensImpl.Lock, EW, RW>
-    }
-}
-
-export class DerivedLensImpl<
-    in out A,
-    in out B,
-    in out ER = never,
-    in out PER = never,
-    in out EW = never,
-    in out PEW = never,
-    in out RR = never,
-    in out PRR = never,
-    in out RW = never,
-    in out PRW = never,
->
-extends LensImpl<A, ER, EW, RR, RW> {
-    constructor(
-        readonly parent: LensImpl<B, PER, PEW, PRR, PRW>,
-        readonly source: DerivedLensImpl.Source<A, B, ER, PER, EW, PEW, RR, PRR, RW, PRW>,
-    ) {
-        super()
-    }
-
-    get resolve() { return this.source.resolve(this.parent.resolve) }
-    get changes() { return this.source.mapStream(this.parent.changes) }
-    get lock() { return this.source.mapLock(this.parent.lock) }
-}
-
-/**
- * Derives a new `Lens` by linking a step to an existing parent lens.
- */
-export const derive: {
-    <A, B, ER, EW, RR, RW, ER2, EW2, RR2, RW2>(
-        self: Lens<B, ER, EW, RR, RW>,
-        source: DerivedLensImpl.Source<A, B, ER2, ER, EW2, EW, RR2, RR, RW2, RW>,
-    ): Lens<A, ER2, EW2, RR2, RW2>
-    <A, B, ER, EW, RR, RW, ER2, EW2, RR2, RW2>(
-        source: DerivedLensImpl.Source<A, B, ER2, ER, EW2, EW, RR2, RR, RW2, RW>,
-    ): (self: Lens<B, ER, EW, RR, RW>) => Lens<A, ER2, EW2, RR2, RW2>
-} = Function.dual(2, <A, B, ER, EW, RR, RW, ER2, EW2, RR2, RW2>(
-    self: Lens<B, ER, EW, RR, RW>,
-    source: DerivedLensImpl.Source<A, B, ER2, ER, EW2, EW, RR2, RR, RW2, RW>,
-): Lens<A, ER2, EW2, RR2, RW2> => new DerivedLensImpl(asLensImpl(self), source))
-
-
 export class UnwrappedLensImpl<in out A, in out ER, in out EW, in out RR, in out RW, in out E1, in out R1>
 extends LensImpl<A, ER | E1, EW | E1, RR | R1, RW | R1> {
     constructor(
@@ -337,6 +276,67 @@ export const fromSubscriptionRef = <A>(
 ): Lens<A, never, never, never, never> => new SubscriptionRefLensImpl(ref as SubscriptionRefLensImpl.SubscriptionRefWithInternals<A>)
 
 
+export declare namespace DerivedLensImpl {
+    export interface Source<
+        in out A,
+        in out B,
+        in out ER = never,
+        in out ESR = never,
+        in out EW = never,
+        in out ESW = never,
+        in out RR = never,
+        in out RSR = never,
+        in out RW = never,
+        in out RSW = never,
+    > {
+        readonly resolve: (effect: Effect.Effect<LensImpl.Resolved<B, ESW, RSW>, ESR, RSR>) => Effect.Effect<LensImpl.Resolved<A, EW, RW>, ER, RR>
+        readonly mapStream: (stream: Stream.Stream<B, ESR, RSR>) => Stream.Stream<A, ER, RR>
+        readonly mapLock: (lock: Effect.Effect<LensImpl.Lock, ESW, RSW>) => Effect.Effect<LensImpl.Lock, EW, RW>
+    }
+}
+
+export class DerivedLensImpl<
+    in out A,
+    in out B,
+    in out ER = never,
+    in out PER = never,
+    in out EW = never,
+    in out PEW = never,
+    in out RR = never,
+    in out PRR = never,
+    in out RW = never,
+    in out PRW = never,
+>
+extends LensImpl<A, ER, EW, RR, RW> {
+    constructor(
+        readonly parent: LensImpl<B, PER, PEW, PRR, PRW>,
+        readonly source: DerivedLensImpl.Source<A, B, ER, PER, EW, PEW, RR, PRR, RW, PRW>,
+    ) {
+        super()
+    }
+
+    get resolve() { return this.source.resolve(this.parent.resolve) }
+    get changes() { return this.source.mapStream(this.parent.changes) }
+    get lock() { return this.source.mapLock(this.parent.lock) }
+}
+
+/**
+ * Derives a new `Lens` by linking a step to an existing parent lens.
+ */
+export const derive: {
+    <A, B, ER, EW, RR, RW, ER2, EW2, RR2, RW2>(
+        self: Lens<B, ER, EW, RR, RW>,
+        source: DerivedLensImpl.Source<A, B, ER2, ER, EW2, EW, RR2, RR, RW2, RW>,
+    ): Lens<A, ER2, EW2, RR2, RW2>
+    <A, B, ER, EW, RR, RW, ER2, EW2, RR2, RW2>(
+        source: DerivedLensImpl.Source<A, B, ER2, ER, EW2, EW, RR2, RR, RW2, RW>,
+    ): (self: Lens<B, ER, EW, RR, RW>) => Lens<A, ER2, EW2, RR2, RW2>
+} = Function.dual(2, <A, B, ER, EW, RR, RW, ER2, EW2, RR2, RW2>(
+    self: Lens<B, ER, EW, RR, RW>,
+    source: DerivedLensImpl.Source<A, B, ER2, ER, EW2, EW, RR2, RR, RW2, RW>,
+): Lens<A, ER2, EW2, RR2, RW2> => new DerivedLensImpl(asLensImpl(self), source))
+
+
 /**
  * Derives a new `Lens` by applying synchronous getters and setters over the focused value.
  */