diff --git a/packages/engine.io-client/lib/socket.ts b/packages/engine.io-client/lib/socket.ts
index 645a43622e..3449a0ecd7 100644
--- a/packages/engine.io-client/lib/socket.ts
+++ b/packages/engine.io-client/lib/socket.ts
@@ -1167,7 +1167,7 @@ export class Socket extends SocketWithUpgrade {
   constructor(uri?: string, opts?: SocketOptions);
   constructor(opts: SocketOptions);
   constructor(uri?: string | SocketOptions, opts: SocketOptions = {}) {
-    const o = typeof uri === "object" ? uri : opts;
+    const o = typeof uri === "object" ? { ...uri } : { ...opts };
 
     if (
       !o.transports ||
diff --git a/packages/engine.io-client/test/socket.js b/packages/engine.io-client/test/socket.js
index 9e87e36170..440491005b 100644
--- a/packages/engine.io-client/test/socket.js
+++ b/packages/engine.io-client/test/socket.js
@@ -23,6 +23,14 @@ describe("Socket", function () {
     });
   });
 
+  it("should not mutate the options object", () => {
+    const options = { transports: ["websocket", "polling"] };
+    const originalTransports = [...options.transports];
+    const socket = new Socket(options);
+    expect(options.transports).to.eql(originalTransports);
+    socket.close();
+  });
+
   it("throws an error when no transports are available", (done) => {
     const socket = new Socket({ transports: [] });
     let errorMessage = "";