diff --git a/index.ts b/index.ts
index 1df3ed8..831147e 100644
--- a/index.ts
+++ b/index.ts
@@ -19,11 +19,11 @@ interface Options {
 }
 
 class Client {
-  source: string;
-  target: string;
-  fetch: typeof global.fetch;
-  logger: Pick<Console, Severity>;
-  events!: EventSource;
+  #source: string;
+  #target: string;
+  #fetch: typeof global.fetch;
+  #logger: Pick<Console, Severity>;
+  #events!: EventSource;
 
   constructor({
     source,
@@ -31,10 +31,10 @@ class Client {
     logger = console,
     fetch = undiciFetch,
   }: Options) {
-    this.source = source;
-    this.target = target;
-    this.logger = logger!;
-    this.fetch = fetch;
+    this.#source = source;
+    this.#target = target;
+    this.#logger = logger!;
+    this.#fetch = fetch;
 
     if (!validator.isURL(this.source)) {
       throw new Error("The provided URL is invalid.");
@@ -57,7 +57,7 @@ class Client {
   async onmessage(msg: MessageEvent<string>) {
     const data = JSON.parse(msg.data);
 
-    const target = url.parse(this.target, true);
+    const target = url.parse(this.#target, true);
     const mergedQuery = { ...target.query, ...data.query };
     target.search = querystring.stringify(mergedQuery);
 
@@ -80,28 +80,28 @@ class Client {
     headers["content-type"] = "application/json";
 
     try {
-      const response = await this.fetch(url.format(target), {
+      const response = await this.#fetch(url.format(target), {
         method: "POST",
         mode: data["sec-fetch-mode"],
         body,
         headers,
       });
-      this.logger.info(`POST ${response.url} - ${response.status}`);
+      this.#logger.info(`POST ${response.url} - ${response.status}`);
     } catch (err) {
-      this.logger.error(err);
+      this.#logger.error(err);
     }
   }
 
   onopen() {
-    this.logger.info("Connected", this.events.url);
+    this.#logger.info("Connected", this.events.url);
   }
 
   onerror(err: ErrorEvent) {
-    this.logger.error(err);
+    this.#logger.error(err);
   }
 
   start() {
-    const events = new EventSource(this.source, {
+    const events = new EventSource(this.#source, {
       dispatcher: new EnvHttpProxyAgent(),
     });
 
@@ -112,8 +112,8 @@ class Client {
     events.addEventListener("open", this.onopen.bind(this));
     events.addEventListener("error", this.onerror.bind(this));
 
-    this.logger.info(`Forwarding ${this.source} to ${this.target}`);
-    this.events = events;
+    this.#logger.info(`Forwarding ${this.#source} to ${this.#target}`);
+    this.#events = events;
 
     return events;
   }