diff --git a/src/utils/async-queue.ts b/src/utils/async-queue.ts
index df748f7..4e90b6f 100644
--- a/src/utils/async-queue.ts
+++ b/src/utils/async-queue.ts
@@ -1,10 +1,8 @@
 import { DoubleQueue } from './double-queue';
 import type { Future } from './types';
-
 export class AsyncQueue<T> {
-  static CancelledError = class CancelledError extends Error {};
   protected _queue: DoubleQueue<T>;
-  protected _getterFutures = new DoubleQueue<Future<T>>();
+  protected _getters = new DoubleQueue<Future<T>>();
 
   constructor(iterable: Iterable<T> = []) {
     this._queue = new DoubleQueue(iterable);
@@ -19,13 +17,13 @@ export class AsyncQueue<T> {
       return this._queue.shift() as T;
     }
     const future: Future<T> = Promise.withResolvers();
-    this._getterFutures.push(future);
+    this._getters.push(future);
     return future.promise;
   }
 
   push(...values: T[]): this {
     for (const value of values) {
-      const future = this._getterFutures.shift();
+      const future = this._getters.shift();
       if (future !== undefined) {
         future.resolve(value);
       } else {
@@ -36,8 +34,12 @@ export class AsyncQueue<T> {
   }
 
   cancelGetters() {
-    for (const future of this._getterFutures) {
+    for (const future of this._getters) {
       future.reject(new AsyncQueue.CancelledError());
     }
   }
 }
+
+export namespace AsyncQueue {
+  export class CancelledError extends Error {}
+}