diff --git a/atom/browser/api/event_emitter.cc b/atom/browser/api/event_emitter.cc
index 9cf7ba520c0f..46a8e629e3f3 100644
--- a/atom/browser/api/event_emitter.cc
+++ b/atom/browser/api/event_emitter.cc
@@ -6,6 +6,7 @@
 
 #include "atom/browser/api/event.h"
 #include "native_mate/arguments.h"
+#include "native_mate/dictionary.h"
 #include "native_mate/object_template_builder.h"
 
 namespace mate {
@@ -15,8 +16,8 @@ namespace {
 v8::Persistent<v8::ObjectTemplate> event_template;
 
 void PreventDefault(mate::Arguments* args) {
-  args->GetThis()->Set(StringToV8(args->isolate(), "defaultPrevented"),
-                       v8::True(args->isolate()));
+  mate::Dictionary self(args->isolate(), args->GetThis());
+  self.Set("defaultPrevented", true);
 }
 
 // Create a pure JavaScript Event object.
@@ -38,7 +39,7 @@ EventEmitter::EventEmitter() {
 
 v8::Local<v8::Object> EventEmitter::CreateEvent(v8::Isolate* isolate,
                                                 content::WebContents* sender,
-                                                IPC::Message* message) const {
+                                                IPC::Message* message) {
   v8::Local<v8::Object> event;
   bool use_native_event = sender && message;
 
@@ -49,6 +50,7 @@ v8::Local<v8::Object> EventEmitter::CreateEvent(v8::Isolate* isolate,
   } else {
     event = CreateEventObject(isolate);
   }
+  mate::Dictionary(isolate, event).Set("sender", GetWrapper(isolate));
   return event;
 }
 
diff --git a/atom/browser/api/event_emitter.h b/atom/browser/api/event_emitter.h
index a249ce23f087..43fbd84f61c4 100644
--- a/atom/browser/api/event_emitter.h
+++ b/atom/browser/api/event_emitter.h
@@ -51,7 +51,7 @@ class EventEmitter : public Wrappable {
  private:
   v8::Local<v8::Object> CreateEvent(v8::Isolate* isolate,
                                     content::WebContents* sender,
-                                    IPC::Message* message) const;
+                                    IPC::Message* message);
 
   DISALLOW_COPY_AND_ASSIGN(EventEmitter);
 };
diff --git a/atom/browser/api/lib/web-contents.coffee b/atom/browser/api/lib/web-contents.coffee
index c07c54103385..b2232b72cda6 100644
--- a/atom/browser/api/lib/web-contents.coffee
+++ b/atom/browser/api/lib/web-contents.coffee
@@ -33,12 +33,10 @@ wrapWebContents = (webContents) ->
   # Dispatch IPC messages to the ipc module.
   webContents.on 'ipc-message', (event, packed) ->
     [channel, args...] = packed
-    Object.defineProperty event, 'sender', value: webContents
     ipc.emit channel, event, args...
   webContents.on 'ipc-message-sync', (event, packed) ->
     [channel, args...] = packed
     Object.defineProperty event, 'returnValue', set: (value) -> event.sendReply JSON.stringify(value)
-    Object.defineProperty event, 'sender', value: webContents
     ipc.emit channel, event, args...
 
   webContents.printToPDF = (options, callback) ->