diff --git a/types/opossum/index.d.ts b/types/opossum/index.d.ts
index b955f940e3..e79a9c4bba 100644
--- a/types/opossum/index.d.ts
+++ b/types/opossum/index.d.ts
@@ -1,23 +1,26 @@
 // Type definitions for opossum 1.9
 // Project: https://github.com/nodeshift/opossum
 // Definitions by: Quinn Langille <https://github.com/quinnlangille>
+//                 Willy Zhang <https://github.com/merufm>
 //                 Lance Ball <https://github.com/lance>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.8
 
 /// <reference types="node"/>
 import * as stream from "stream";
+import { EventEmitter } from "events";
 
-export type Action = () => any;
+export type Action = (...args: any[]) => any;
 
-export class CircuitBreaker {
+export class CircuitBreaker extends EventEmitter {
     clearCache(): void;
     close(): void;
     disable(): void;
     enable(): void;
-    fallback(): CircuitBreaker;
-    fire(): Promise<any>;
-    healthCheck(func: () => Promise<any>, interval: number): Promise<any>;
+    fallback(func?: (...args: any[]) => any): this;
+    fire(...args: any[]): Promise<any>;
+    healthCheck(func: (...args: any[]) => Promise<any>, interval?: number): Promise<any>;
+    on(event: string | symbol, listener: (...args: any[]) => void): this;
     open(): void;
     promisify(action: Action): Promise<Action>;
     stats(): stream.Transform;
@@ -35,6 +38,22 @@ export class CircuitBreaker {
     static readonly volumeThreshold: symbol;
 }
 
+export enum Event {
+    cacheHit = 'cacheHit',
+    cacheMiss = 'cacheMiss',
+    close = 'close',
+    failure = 'failure',
+    fallback = 'fallback',
+    fire = 'fire',
+    halfOpen = 'halfOpen',
+    healthCheckFailed = 'health-check-failed',
+    open = 'open',
+    reject = 'reject',
+    semaphoreLocked = 'semaphore-locked',
+    success = 'success',
+    timeout = 'timeout'
+}
+
 export interface CircuitBreakerOptions {
     timeout?: number;
     maxFailures?: number;