diff --git a/browser-harness/browser-harness.d.ts b/browser-harness/browser-harness.d.ts
index 3b8cf08be..8c410b94a 100644
--- a/browser-harness/browser-harness.d.ts
+++ b/browser-harness/browser-harness.d.ts
@@ -9,25 +9,25 @@ declare module "browser-harness" {
     import events = require("events");
 
     interface HarnessEvents extends events.NodeEventEmitter {
-        once(event: string, listener: (driver: Driver) => void);
-        once(event: 'ready', listener: (driver: Driver) => void);
+        once(event: string, listener: (driver: Driver) => void): events.NodeEventEmitter;
+        once(event: 'ready', listener: (driver: Driver) => void): events.NodeEventEmitter;
 
-        on(event: string, listener: (driver: Driver) => void);
-        on(event: 'ready', listener: (driver: Driver) => void);
+        on(event: string, listener: (driver: Driver) => void): events.NodeEventEmitter;
+        on(event: 'ready', listener: (driver: Driver) => void): events.NodeEventEmitter;
     }
 
     interface DriverEvents extends events.NodeEventEmitter {
-        once(event: string, listener: (text: string) => void);
-        once(event: 'console.log', listener: (text: string) => void);
-        once(event: 'console.warn', listener: (text: string) => void);
-        once(event: 'console.error', listener: (text: string) => void);
-        once(event: 'window.onerror', listener: (text: string) => void);
+        once(event: string, listener: (text: string) => void): events.NodeEventEmitter;
+        once(event: 'console.log', listener: (text: string) => void): events.NodeEventEmitter;
+        once(event: 'console.warn', listener: (text: string) => void): events.NodeEventEmitter;
+        once(event: 'console.error', listener: (text: string) => void): events.NodeEventEmitter;
+        once(event: 'window.onerror', listener: (text: string) => void): events.NodeEventEmitter;
 
-        on(event: string, listener: (text: string) => void);
-        on(event: 'console.log', listener: (text: string) => void);
-        on(event: 'console.warn', listener: (text: string) => void);
-        on(event: 'console.error', listener: (text: string) => void);
-        on(event: 'window.onerror', listener: (text: string) => void);
+        on(event: string, listener: (text: string) => void): events.NodeEventEmitter;
+        on(event: 'console.log', listener: (text: string) => void): events.NodeEventEmitter;
+        on(event: 'console.warn', listener: (text: string) => void): events.NodeEventEmitter;
+        on(event: 'console.error', listener: (text: string) => void): events.NodeEventEmitter;
+        on(event: 'window.onerror', listener: (text: string) => void): events.NodeEventEmitter;
     }
 
     export interface Driver {