diff --git a/packages/effect/src/internal/effect/circular.ts b/packages/effect/src/internal/effect/circular.ts
index f35a41a706..7c8d2e5e04 100644
--- a/packages/effect/src/internal/effect/circular.ts
+++ b/packages/effect/src/internal/effect/circular.ts
@@ -35,7 +35,7 @@ import * as supervisor from "../supervisor.js"
 
 /** @internal */
 class Semaphore {
-  public waiters = new Array<() => boolean>()
+  public waiters = new Set<() => boolean>()
   public taken = 0
 
   constructor(readonly permits: number) {}
@@ -51,20 +51,14 @@ class Semaphore {
           if (this.free < n) {
             return false
           }
-          const observerIndex = this.waiters.findIndex((cb) => cb === observer)
-          if (observerIndex !== -1) {
-            this.waiters.splice(observerIndex, 1)
-          }
+          this.waiters.delete(observer)
           this.taken += n
           resume(core.succeed(n))
           return true
         }
-        this.waiters.push(observer)
+        this.waiters.add(observer)
         return Either.left(core.sync(() => {
-          const observerIndex = this.waiters.findIndex((cb) => cb === observer)
-          if (observerIndex !== -1) {
-            this.waiters.splice(observerIndex, 1)
-          }
+          this.waiters.delete(observer)
         }))
       }
       this.taken += n
@@ -75,8 +69,8 @@ class Semaphore {
     core.withFiberRuntime<never, never, void>((fiber) => {
       this.taken = f(this.taken)
       fiber.getFiberRef(currentScheduler).scheduleTask(() => {
-        while (this.waiters.length > 0) {
-          if (this.waiters[0]() === false) {
+        for (const waiter of this.waiters) {
+          if (waiter() === false) {
             break
           }
         }