diff --git a/lib/binary.ts b/lib/binary.ts
index 80a6b96..89956c2 100644
--- a/lib/binary.ts
+++ b/lib/binary.ts
@@ -1,4 +1,4 @@
-import isBinary from "./is-binary";
+import { isBinary } from "./is-binary";
 
 /**
  * Replaces every Buffer | ArrayBuffer | Blob | File in packet with a numbered placeholder.
diff --git a/lib/index.ts b/lib/index.ts
index ff5671e..cc6e69d 100644
--- a/lib/index.ts
+++ b/lib/index.ts
@@ -1,6 +1,6 @@
-import Emitter from "component-emitter";
+import Emitter = require("component-emitter");
 import { deconstructPacket, reconstructPacket } from "./binary";
-import isBinary from "./is-binary";
+import { isBinary, hasBinary } from "./is-binary";
 
 const debug = require("debug")("socket.io-parser");
 
@@ -44,15 +44,16 @@ export class Encoder {
   public encode(obj: Packet) {
     debug("encoding packet %j", obj);
 
-    if (
-      obj.type === PacketType.BINARY_EVENT ||
-      obj.type === PacketType.BINARY_ACK
-    ) {
-      return this.encodeAsBinary(obj);
-    } else {
-      const encoding = this.encodeAsString(obj);
-      return [encoding];
+    if (obj.type === PacketType.EVENT || obj.type === PacketType.ACK) {
+      if (hasBinary(obj)) {
+        obj.type =
+          obj.type === PacketType.EVENT
+            ? PacketType.BINARY_EVENT
+            : PacketType.BINARY_ACK;
+        return this.encodeAsBinary(obj);
+      }
     }
+    return [this.encodeAsString(obj)];
   }
 
   /**
diff --git a/lib/is-binary.ts b/lib/is-binary.ts
index ed8fdbf..0ec6417 100644
--- a/lib/is-binary.ts
+++ b/lib/is-binary.ts
@@ -1,5 +1,3 @@
-const withNativeBuffer: boolean =
-  typeof Buffer === "function" && typeof Buffer.isBuffer === "function";
 const withNativeArrayBuffer: boolean = typeof ArrayBuffer === "function";
 
 const isView = (obj: any) => {
@@ -24,11 +22,45 @@ const withNativeFile =
  * @private
  */
 
-export default function isBinary(obj: any) {
+export function isBinary(obj: any) {
   return (
-    (withNativeBuffer && Buffer.isBuffer(obj)) ||
     (withNativeArrayBuffer && (obj instanceof ArrayBuffer || isView(obj))) ||
     (withNativeBlob && obj instanceof Blob) ||
     (withNativeFile && obj instanceof File)
   );
 }
+
+export function hasBinary(obj: any, toJSON?: boolean) {
+  if (!obj || typeof obj !== "object") {
+    return false;
+  }
+
+  if (Array.isArray(obj)) {
+    for (let i = 0, l = obj.length; i < l; i++) {
+      if (hasBinary(obj[i])) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  if (isBinary(obj)) {
+    return true;
+  }
+
+  if (
+    obj.toJSON &&
+    typeof obj.toJSON === "function" &&
+    arguments.length === 1
+  ) {
+    return hasBinary(obj.toJSON(), true);
+  }
+
+  for (const key in obj) {
+    if (Object.prototype.hasOwnProperty.call(obj, key) && hasBinary(obj[key])) {
+      return true;
+    }
+  }
+
+  return false;
+}
diff --git a/test/arraybuffer.js b/test/arraybuffer.js
index 14ef58c..6d44057 100644
--- a/test/arraybuffer.js
+++ b/test/arraybuffer.js
@@ -6,7 +6,7 @@ const encoder = new Encoder();
 describe("parser", () => {
   it("encodes an ArrayBuffer", (done) => {
     const packet = {
-      type: PacketType.BINARY_EVENT,
+      type: PacketType.EVENT,
       data: ["a", new ArrayBuffer(2)],
       id: 0,
       nsp: "/",
@@ -19,7 +19,7 @@ describe("parser", () => {
     for (let i = 0; i < array.length; i++) array[i] = i;
 
     const packet = {
-      type: PacketType.BINARY_EVENT,
+      type: PacketType.EVENT,
       data: ["a", array],
       id: 0,
       nsp: "/",
@@ -29,7 +29,7 @@ describe("parser", () => {
 
   it("encodes ArrayBuffers deep in JSON", (done) => {
     const packet = {
-      type: PacketType.BINARY_EVENT,
+      type: PacketType.EVENT,
       data: [
         "a",
         {
@@ -46,7 +46,7 @@ describe("parser", () => {
 
   it("encodes deep binary JSON with null values", (done) => {
     const packet = {
-      type: PacketType.BINARY_EVENT,
+      type: PacketType.EVENT,
       data: ["a", { a: "b", c: 4, e: { g: null }, h: new ArrayBuffer(9) }],
       nsp: "/",
       id: 600,
@@ -56,7 +56,7 @@ describe("parser", () => {
 
   it("cleans itself up on close", () => {
     const packet = {
-      type: PacketType.BINARY_EVENT,
+      type: PacketType.EVENT,
       data: ["a", new ArrayBuffer(2), new ArrayBuffer(3)],
       id: 0,
       nsp: "/",
diff --git a/test/blob.js b/test/blob.js
index 559d7ef..cf0717a 100644
--- a/test/blob.js
+++ b/test/blob.js
@@ -24,7 +24,7 @@ describe("parser", () => {
     }
 
     const packet = {
-      type: PacketType.BINARY_EVENT,
+      type: PacketType.EVENT,
       data: ["a", data],
       id: 0,
       nsp: "/",
@@ -43,7 +43,7 @@ describe("parser", () => {
     }
 
     const packet = {
-      type: PacketType.BINARY_EVENT,
+      type: PacketType.EVENT,
       data: ["a", { a: "hi", b: { why: data }, c: "bye" }],
       id: 999,
       nsp: "/deep",
@@ -62,7 +62,7 @@ describe("parser", () => {
     }
 
     const packet = {
-      type: PacketType.BINARY_ACK,
+      type: PacketType.ACK,
       data: [{ a: "hi ack", b: { why: data }, c: "bye ack" }],
       id: 999,
       nsp: "/deep",
diff --git a/test/buffer.js b/test/buffer.js
index d5ebc23..af8e1ba 100644
--- a/test/buffer.js
+++ b/test/buffer.js
@@ -5,7 +5,7 @@ describe("parser", () => {
   it("encodes a Buffer", (done) => {
     helpers.test_bin(
       {
-        type: PacketType.BINARY_EVENT,
+        type: PacketType.EVENT,
         data: ["a", Buffer.from("abc", "utf8")],
         id: 23,
         nsp: "/cool",
@@ -17,7 +17,7 @@ describe("parser", () => {
   it("encodes a binary ack with Buffer", (done) => {
     helpers.test_bin(
       {
-        type: PacketType.BINARY_ACK,
+        type: PacketType.ACK,
         data: ["a", Buffer.from("xxx", "utf8"), {}],
         id: 127,
         nsp: "/back",
diff --git a/tsconfig.json b/tsconfig.json
index bcd6128..87d51bf 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -4,8 +4,7 @@
     "allowJs": false,
     "target": "es2017",
     "module": "commonjs",
-    "declaration": true,
-    "esModuleInterop": true
+    "declaration": true
   },
   "include": [
     "./lib/**/*"