diff --git a/src/cache.ts b/src/cache.ts
index be9bf6688f..b8b1e89818 100644
--- a/src/cache.ts
+++ b/src/cache.ts
@@ -71,13 +71,16 @@ export class ListWatch<T extends KubernetesObject> implements ObjectCache<T>, In
         this._stop();
     }
 
-    public on(verb: 'add' | 'update' | 'delete' | 'change', cb: ObjectCallback<T>): void;
-    public on(verb: 'error' | 'connect', cb: ErrorCallback): void;
-    public on(verb: string, cb: any): void {
+    public on(verb: ADD | UPDATE | DELETE | CHANGE, cb: ObjectCallback<T>): void;
+    public on(verb: ERROR | CONNECT, cb: ErrorCallback): void;
+    public on(
+        verb: ADD | UPDATE | DELETE | CHANGE | ERROR | CONNECT,
+        cb: ObjectCallback<T> | ErrorCallback,
+    ): void {
         if (verb === CHANGE) {
-            this.on('add', cb);
-            this.on('update', cb);
-            this.on('delete', cb);
+            this.on(ADD, cb);
+            this.on(UPDATE, cb);
+            this.on(DELETE, cb);
             return;
         }
         if (this.callbackCache[verb] === undefined) {
diff --git a/src/informer.ts b/src/informer.ts
index eb67bbd8db..714ff4fe57 100644
--- a/src/informer.ts
+++ b/src/informer.ts
@@ -9,19 +9,27 @@ export type ListCallback<T extends KubernetesObject> = (list: T[], ResourceVersi
 export type ListPromise<T extends KubernetesObject> = () => Promise<KubernetesListObject<T>>;
 
 // These are issued per object
-export const ADD: string = 'add';
-export const UPDATE: string = 'update';
-export const CHANGE: string = 'change';
-export const DELETE: string = 'delete';
+export const ADD = 'add';
+export type ADD = typeof ADD;
+export const UPDATE = 'update';
+export type UPDATE = typeof UPDATE;
+export const CHANGE = 'change';
+export type CHANGE = typeof CHANGE;
+export const DELETE = 'delete';
+export type DELETE = typeof DELETE;
 
 // This is issued when a watch connects or reconnects
-export const CONNECT: string = 'connect';
+export const CONNECT = 'connect';
+export type CONNECT = typeof CONNECT;
 // This is issued when there is an error
-export const ERROR: string = 'error';
+export const ERROR = 'error';
+export type ERROR = typeof ERROR;
 
 export interface Informer<T extends KubernetesObject> {
-    on(verb: string, fn: ObjectCallback<T>): void;
-    off(verb: string, fn: ObjectCallback<T>): void;
+    on(verb: ADD | UPDATE | DELETE | CHANGE, cb: ObjectCallback<T>): void;
+    on(verb: ERROR | CONNECT, cb: ErrorCallback): void;
+    off(verb: ADD | UPDATE | DELETE | CHANGE, cb: ObjectCallback<T>): void;
+    off(verb: ERROR | CONNECT, cb: ErrorCallback): void;
     start(): Promise<void>;
     stop(): Promise<void>;
 }