diff --git a/index.d.ts b/index.d.ts
index fe48e0f..53be419 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1,11 +1,43 @@
-import { Duplex } from 'stream'
+import { Duplex, Readable } from 'stream'
 
 declare class FileType extends Duplex {
-  fileTypePromise(): Promise<FileType.FileTypeResult>
+  fileTypePromise(): Promise<FileType.FileTypeResult | null>
 
-  addListener(event: 'file-type', listener: (fileType: FileType.FileTypeResult) => void): this
-  on(event: 'file-type', listener: (fileType: FileType.FileTypeResult) => void): this
-  once(event: 'file-type', listener: (fileType: FileType.FileTypeResult) => void): this
+  addListener(event: 'close', listener: () => void): this
+  addListener(event: 'data', listener: (chunk: any) => void): this
+  addListener(event: 'drain', listener: () => void): this
+  addListener(event: 'end', listener: () => void): this
+  addListener(event: 'error', listener: (err: Error) => void): this
+  addListener(event: 'file-type', listener: (fileType: FileType.FileTypeResult | null) => void): this
+  addListener(event: 'finish', listener: () => void): this
+  addListener(event: 'pipe', listener: (src: Readable) => void): this
+  addListener(event: 'readable', listener: () => void): this
+  addListener(event: 'unpipe', listener: (src: Readable) => void): this
+  addListener(event: string | symbol, listener: (...args: any[]) => void): this;
+
+  on(event: 'close', listener: () => void): this
+  on(event: 'data', listener: (chunk: any) => void): this
+  on(event: 'drain', listener: () => void): this
+  on(event: 'end', listener: () => void): this
+  on(event: 'error', listener: (err: Error) => void): this
+  on(event: 'file-type', listener: (fileType: FileType.FileTypeResult | null) => void): this
+  on(event: 'finish', listener: () => void): this
+  on(event: 'pipe', listener: (src: Readable) => void): this
+  on(event: 'readable', listener: () => void): this
+  on(event: 'unpipe', listener: (src: Readable) => void): this
+  on(event: string | symbol, listener: (...args: any[]) => void): this;
+
+  once(event: 'close', listener: () => void): this
+  once(event: 'data', listener: (chunk: any) => void): this
+  once(event: 'drain', listener: () => void): this
+  once(event: 'end', listener: () => void): this
+  once(event: 'error', listener: (err: Error) => void): this
+  once(event: 'file-type', listener: (fileType: FileType.FileTypeResult | null) => void): this
+  once(event: 'finish', listener: () => void): this
+  once(event: 'pipe', listener: (src: Readable) => void): this
+  once(event: 'readable', listener: () => void): this
+  once(event: 'unpipe', listener: (src: Readable) => void): this
+  once(event: string | symbol, listener: (...args: any[]) => void): this;
 }
 
 declare namespace FileType {