diff --git a/deno.lock b/deno.lock
new file mode 100644
index 0000000..5b0da6c
--- /dev/null
+++ b/deno.lock
@@ -0,0 +1,31 @@
+{
+  "version": "3",
+  "packages": {
+    "specifiers": {
+      "jsr:@std/assert@^1.0.2": "jsr:@std/assert@1.0.2",
+      "jsr:@std/async@^1.0.2": "jsr:@std/async@1.0.2",
+      "jsr:@std/internal@^1.0.1": "jsr:@std/internal@1.0.1"
+    },
+    "jsr": {
+      "@std/assert@1.0.2": {
+        "integrity": "ccacec332958126deaceb5c63ff8b4eaf9f5ed0eac9feccf124110435e59e49c",
+        "dependencies": [
+          "jsr:@std/internal@^1.0.1"
+        ]
+      },
+      "@std/async@1.0.2": {
+        "integrity": "36e7f0f922c843b45df546857d269f01ed4d0406aced2a6639eac325b2435e43"
+      },
+      "@std/internal@1.0.1": {
+        "integrity": "6f8c7544d06a11dd256c8d6ba54b11ed870aac6c5aeafff499892662c57673e6"
+      }
+    }
+  },
+  "remote": {},
+  "workspace": {
+    "dependencies": [
+      "jsr:@std/assert@^1.0.2",
+      "jsr:@std/async@^1.0.2"
+    ]
+  }
+}
diff --git a/mutex.ts b/mutex.ts
index 4851dbb..92c8133 100644
--- a/mutex.ts
+++ b/mutex.ts
@@ -26,13 +26,13 @@
  * ```
  */
 export class Mutex {
-  #waiters: Promise<void>[] = [];
+  #waiters: Set<Promise<void>> = new Set();
 
   /**
    * Returns true if the mutex is locked, false otherwise.
    */
   get locked(): boolean {
-    return this.#waiters.length > 0;
+    return this.#waiters.size > 0;
   }
 
   /**
@@ -43,10 +43,11 @@ export class Mutex {
   acquire(): Promise<Disposable> & Disposable {
     const waiters = [...this.#waiters];
     const { promise, resolve } = Promise.withResolvers<void>();
-    this.#waiters.push(promise);
+    this.#waiters.add(promise);
     const disposable = {
       [Symbol.dispose]: () => {
         resolve();
+        this.#waiters.delete(promise);
       },
     };
     return Object.assign(