diff --git a/packages/effect-fc/src/Lens.ts b/packages/effect-fc/src/Lens.ts
index 1c1fb62..76533ec 100644
--- a/packages/effect-fc/src/Lens.ts
+++ b/packages/effect-fc/src/Lens.ts
@@ -155,28 +155,21 @@ export const mapStructAt: {
 ))
 
 export const mapArrayAt: {
-    <A, ER, EW, RR, RW>(
-        self: Lens<A[], ER, EW, RR, RW>,
+    <A extends readonly any[], ER, EW, RR, RW>(
+        self: Lens<A, ER, EW, RR, RW>,
         index: number,
-    ): Lens<A, ER | NoSuchElementException, EW | NoSuchElementException, RR, RW>
-    <A, ER, EW, RR, RW>(
-        self: Lens<readonly A[], ER, EW, RR, RW>,
-        index: number,
-    ): Lens<A, ER | NoSuchElementException, EW | NoSuchElementException, RR, RW>
-    <A, ER, EW, RR, RW>(
+    ): Lens<A[number]>
+    <A extends readonly any[], ER, EW, RR, RW>(
         index: number
-    ): (self: Lens<A[], ER, EW, RR, RW>) => Lens<A, ER | NoSuchElementException, EW | NoSuchElementException, RR, RW>
-    <A, ER, EW, RR, RW>(
-        index: number
-    ): (self: Lens<readonly A[], ER, EW, RR, RW>) => Lens<A, ER | NoSuchElementException, EW | NoSuchElementException, RR, RW>
-} = Function.dual(2, <A, ER, EW, RR, RW>(
-    self: Lens<readonly A[], ER, EW, RR, RW>,
+    ): (self: Lens<A, ER, EW, RR, RW>) => Lens<A[number], ER | NoSuchElementException, EW | NoSuchElementException, RR, RW>
+} = Function.dual(2, <A extends readonly any[], ER, EW, RR, RW>(
+    self: Lens<A, ER, EW, RR, RW>,
     index: number,
-): Lens<A, ER | NoSuchElementException, EW | NoSuchElementException, RR, RW> => mapEffect(
+): Lens<A[number], ER | NoSuchElementException, EW | NoSuchElementException, RR, RW> => mapEffect(
     self,
     Array.get(index),
-    (a, b) => Array.replaceOption(a, index, b)),
-)
+    (a, b) => Array.replaceOption(a, index, b) as any,
+))
 
 export const mapMutableArrayAt: {
     <A, ER, EW, RR, RW>(