diff --git a/packages/engine.io-client/lib/transport.ts b/packages/engine.io-client/lib/transport.ts
index ba9407157..ab72c7096 100644
--- a/packages/engine.io-client/lib/transport.ts
+++ b/packages/engine.io-client/lib/transport.ts
@@ -192,7 +192,7 @@ export abstract class Transport extends Emitter<
   private _port() {
     if (
       this.opts.port &&
-      ((this.opts.secure && Number(this.opts.port !== 443)) ||
+      ((this.opts.secure && Number(this.opts.port) !== 443) ||
         (!this.opts.secure && Number(this.opts.port) !== 80))
     ) {
       return ":" + this.opts.port;