diff --git a/packages/effect-fc/src/Form.ts b/packages/effect-fc/src/Form.ts
index c19f782..b339fcc 100644
--- a/packages/effect-fc/src/Form.ts
+++ b/packages/effect-fc/src/Form.ts
@@ -302,14 +302,14 @@ export const focusTupleAt: {
     <P extends readonly PropertyKey[], A extends readonly [any, ...any[]], I extends readonly [any, ...any[]], ER, EW, K extends number>(
         self: Form<P, A, I, ER, EW>,
         index: K,
-    ): Form<readonly [...P, number], A[number], I[number], ER, EW>
+    ): Form<readonly [...P, K], A[K], I[K], ER, EW>
     <P extends readonly PropertyKey[], A extends readonly [any, ...any[]], I extends readonly [any, ...any[]], ER, EW, K extends number>(
         index: K,
-    ): (self: Form<P, A, I, ER, EW>) => Form<readonly [...P, number], A[number], I[number], ER, EW>
+    ): (self: Form<P, A, I, ER, EW>) => Form<readonly [...P, K], A[K], I[K], ER, EW>
 } = Function.dual(2, <P extends readonly PropertyKey[], A extends readonly [any, ...any[]], I extends readonly [any, ...any[]], ER, EW, K extends number>(
     self: Form<P, A, I, ER, EW>,
     index: K,
-): Form<readonly [...P, K], A[number], I[number], ER, EW> => {
+): Form<readonly [...P, K], A[K], I[K], ER, EW> => {
     const form = self as FormImpl<P, A, I, ER, EW>
     const path = [...form.path, index] as const