diff --git a/packages/effect-fc/src/Lens.ts b/packages/effect-fc/src/Lens.ts
index 76533ec..666f5d6 100644
--- a/packages/effect-fc/src/Lens.ts
+++ b/packages/effect-fc/src/Lens.ts
@@ -68,7 +68,9 @@ export const fromSubscriptionRef = <A>(
 ): Lens<A, never, never, never, never> => make({
     get get() { return ref.get },
     get changes() { return ref.changes },
-    modify: ref.modifyEffect.bind(ref), // TODO
+    modify: <B, E1 = never, R1 = never>(
+        f: (a: A) => Effect.Effect<readonly [B, A], E1, R1>
+    ) => ref.modifyEffect(f),
 })
 
 export const unwrap = <A, ER, EW, RR, RW, E1, R1>(