diff --git a/widget/cocoa/OSXNotificationCenter.h b/widget/cocoa/OSXNotificationCenter.h
index 3ae5df5b4487..f56ddd2762e7 100644
--- a/widget/cocoa/OSXNotificationCenter.h
+++ b/widget/cocoa/OSXNotificationCenter.h
@@ -25,13 +25,15 @@ class OSXNotificationInfo;
 
 class OSXNotificationCenter : public nsIAlertsService,
                               public imgINotificationObserver,
-                              public nsITimerCallback
+                              public nsITimerCallback,
+                              public nsIAlertsIconData
 {
 public:
   NS_DECL_ISUPPORTS
   NS_DECL_NSIALERTSSERVICE
   NS_DECL_IMGINOTIFICATIONOBSERVER
   NS_DECL_NSITIMERCALLBACK
+  NS_DECL_NSIALERTSICONDATA
 
   OSXNotificationCenter();
 
diff --git a/widget/cocoa/OSXNotificationCenter.mm b/widget/cocoa/OSXNotificationCenter.mm
index 54e51886f626..2fee40b40d63 100644
--- a/widget/cocoa/OSXNotificationCenter.mm
+++ b/widget/cocoa/OSXNotificationCenter.mm
@@ -218,7 +218,8 @@ OSXNotificationCenter::~OSXNotificationCenter()
   NS_OBJC_END_TRY_ABORT_BLOCK;
 }
 
-NS_IMPL_ISUPPORTS(OSXNotificationCenter, nsIAlertsService, imgINotificationObserver, nsITimerCallback)
+NS_IMPL_ISUPPORTS(OSXNotificationCenter, nsIAlertsService, nsITimerCallback,
+                  imgINotificationObserver, nsIAlertsIconData)
 
 nsresult OSXNotificationCenter::Init()
 {
@@ -255,6 +256,15 @@ OSXNotificationCenter::ShowAlertNotification(const nsAString & aImageUrl, const
 NS_IMETHODIMP
 OSXNotificationCenter::ShowAlert(nsIAlertNotification* aAlert,
                                  nsIObserver* aAlertListener)
+{
+  return ShowAlertWithIconData(aAlert, aAlertListener, 0, nullptr);
+}
+
+NS_IMETHODIMP
+OSXNotificationCenter::ShowAlertWithIconData(nsIAlertNotification* aAlert,
+                                             nsIObserver* aAlertListener,
+                                             uint32_t aIconSize,
+                                             const uint8_t* aIconData)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;
 
@@ -348,6 +358,18 @@ OSXNotificationCenter::ShowAlert(nsIAlertNotification* aAlert,
 
   OSXNotificationInfo *osxni = new OSXNotificationInfo(alertName, aAlertListener, cookie);
 
+  // Show the favicon if supported on this version of OS X.
+  if (aIconSize > 0 &&
+      [notification respondsToSelector:@selector(set_identityImage:)] &&
+      [notification respondsToSelector:@selector(set_identityImageHasBorder:)]) {
+
+    NSData *iconData = [NSData dataWithBytes:aIconData length:aIconSize];
+    NSImage *icon = [[[NSImage alloc] initWithData:iconData] autorelease];
+
+    [(NSObject*)notification setValue:icon forKey:@"_identityImage"];
+    [(NSObject*)notification setValue:@(NO) forKey:@"_identityImageHasBorder"];
+  }
+
   nsAutoString imageUrl;
   rv = aAlert->GetImageURL(imageUrl);
   NS_ENSURE_SUCCESS(rv, rv);