diff --git a/dom/base/nsGkAtomList.h b/dom/base/nsGkAtomList.h
index af25f97e1c..9622b21d3e 100644
--- a/dom/base/nsGkAtomList.h
+++ b/dom/base/nsGkAtomList.h
@@ -908,6 +908,7 @@ GK_ATOM(onreadsuccess, "onreadsuccess")
 GK_ATOM(onready, "onready")
 GK_ATOM(onreadystatechange, "onreadystatechange")
 GK_ATOM(onreceived, "onreceived")
+GK_ATOM(onrejectionhandled, "onrejectionhandled")
 GK_ATOM(onremoteheld, "onremoteheld")
 GK_ATOM(onremoteresumed, "onremoteresumed")
 GK_ATOM(onrequestprogress, "onrequestprogress")
@@ -951,6 +952,7 @@ GK_ATOM(ontransitionend, "ontransitionend")
 GK_ATOM(ontransitionrun, "ontransitionrun")
 GK_ATOM(ontransitionstart, "ontransitionstart")
 GK_ATOM(onunderflow, "onunderflow")
+GK_ATOM(onunhandledrejection, "onunhandledrejection")
 GK_ATOM(onunload, "onunload")
 GK_ATOM(onupdatefound, "onupdatefound")
 GK_ATOM(onupdateready, "onupdateready")
diff --git a/dom/events/EventNameList.h b/dom/events/EventNameList.h
index c4edc1fe2a..0a17b5f147 100644
--- a/dom/events/EventNameList.h
+++ b/dom/events/EventNameList.h
@@ -578,14 +578,14 @@ WINDOW_EVENT(popstate,
              ePopState,
              EventNameType_XUL | EventNameType_HTMLBodyOrFramesetOnly,
              eBasicEventClass)
-// Not supported yet
-// WINDOW_EVENT(redo)
+WINDOW_EVENT(rejectionhandled, eRejectionHandled,
+             EventNameType_HTMLBodyOrFramesetOnly, eBasicEventClass)
 WINDOW_EVENT(storage,
              eStorage,
              EventNameType_HTMLBodyOrFramesetOnly,
              eBasicEventClass)
-// Not supported yet
-// WINDOW_EVENT(undo)
+WINDOW_EVENT(unhandledrejection, eUnhandledRejection,
+             EventNameType_HTMLBodyOrFramesetOnly, eBasicEventClass)
 WINDOW_EVENT(unload,
              eUnload,
              (EventNameType_XUL | EventNameType_SVGSVG |
diff --git a/dom/webidl/EventHandler.webidl b/dom/webidl/EventHandler.webidl
index f7acb66ef4..853067bd6f 100644
--- a/dom/webidl/EventHandler.webidl
+++ b/dom/webidl/EventHandler.webidl
@@ -160,7 +160,9 @@ interface WindowEventHandlers {
            attribute EventHandler onpagehide;
            attribute EventHandler onpageshow;
            attribute EventHandler onpopstate;
+           attribute EventHandler onrejectionhandled;
            attribute EventHandler onstorage;
+           attribute EventHandler onunhandledrejection;
            attribute EventHandler onunload;
 };
 
diff --git a/dom/webidl/WorkerGlobalScope.webidl b/dom/webidl/WorkerGlobalScope.webidl
index 25cfe9e294..7afba6c367 100644
--- a/dom/webidl/WorkerGlobalScope.webidl
+++ b/dom/webidl/WorkerGlobalScope.webidl
@@ -25,6 +25,8 @@ interface WorkerGlobalScope : EventTarget {
 
   attribute EventHandler onoffline;
   attribute EventHandler ononline;
+  attribute EventHandler onrejectionhandled;
+  attribute EventHandler onunhandledrejection;
   // also has additional members in a partial interface
 };
 
diff --git a/dom/workers/WorkerScope.h b/dom/workers/WorkerScope.h
index 81d2733efe..ffbe4fca75 100644
--- a/dom/workers/WorkerScope.h
+++ b/dom/workers/WorkerScope.h
@@ -151,6 +151,8 @@ public:
 
   IMPL_EVENT_HANDLER(online)
   IMPL_EVENT_HANDLER(offline)
+  IMPL_EVENT_HANDLER(rejectionhandled)
+  IMPL_EVENT_HANDLER(unhandledrejection)
 
   void
   Dump(const Optional<nsAString>& aString) const;
diff --git a/widget/EventMessageList.h b/widget/EventMessageList.h
index 7ff16c4841..03ae940dc8 100644
--- a/widget/EventMessageList.h
+++ b/widget/EventMessageList.h
@@ -118,7 +118,9 @@ NS_EVENT_MESSAGE(eImageAbort)
 NS_EVENT_MESSAGE(eLoadError)
 NS_EVENT_MESSAGE(eLoadEnd)
 NS_EVENT_MESSAGE(ePopState)
+NS_EVENT_MESSAGE(eRejectionHandled)
 NS_EVENT_MESSAGE(eStorage)
+NS_EVENT_MESSAGE(eUnhandledRejection)
 NS_EVENT_MESSAGE(eBeforeUnload)
 NS_EVENT_MESSAGE(eReadyStateChange)