diff --git a/dom/webidl/ServiceWorker.webidl b/dom/webidl/ServiceWorker.webidl
index ad0b02ea83a3..a4fe588b783d 100644
--- a/dom/webidl/ServiceWorker.webidl
+++ b/dom/webidl/ServiceWorker.webidl
@@ -8,8 +8,6 @@
  *
  */
 
-// Still unclear what should be subclassed.
-// https://github.com/slightlyoff/ServiceWorker/issues/189
 [Pref="dom.serviceWorkers.enabled",
  // XXXbz I have no idea where this should be exposed.  The spec makes
  // no sense.  But since it's got a pref, let's say window.
@@ -20,6 +18,10 @@ interface ServiceWorker : EventTarget {
 
   readonly attribute ServiceWorkerState state;
   attribute EventHandler onstatechange;
+
+  // FIXME(catalinb): Bug 1053483 - This should be inherited from MessageUtils
+  [Throws]
+  void postMessage(any message, optional sequence<Transferable> transferable);
 };
 
 ServiceWorker implements AbstractWorker;
diff --git a/dom/workers/ServiceWorker.cpp b/dom/workers/ServiceWorker.cpp
index ee2eab96a4a9..f9cbf3820ab7 100644
--- a/dom/workers/ServiceWorker.cpp
+++ b/dom/workers/ServiceWorker.cpp
@@ -11,6 +11,7 @@
 
 #include "mozilla/dom/Promise.h"
 
+using mozilla::ErrorResult;
 using namespace mozilla::dom;
 USING_WORKERS_NAMESPACE
 
@@ -46,6 +47,17 @@ ServiceWorker::WrapObject(JSContext* aCx)
   return ServiceWorkerBinding::Wrap(aCx, this);
 }
 
+void
+ServiceWorker::PostMessage(JSContext* aCx, JS::Handle<JS::Value> aMessage,
+                           const Optional<Sequence<JS::Value>>& aTransferable,
+                           ErrorResult& aRv)
+{
+  WorkerPrivate* workerPrivate = GetWorkerPrivate();
+  MOZ_ASSERT(workerPrivate);
+
+  workerPrivate->PostMessage(aCx, aMessage, aTransferable, aRv);
+}
+
 WorkerPrivate*
 ServiceWorker::GetWorkerPrivate() const
 {
diff --git a/dom/workers/ServiceWorker.h b/dom/workers/ServiceWorker.h
index 0883ad525b81..3c3b7e612abd 100644
--- a/dom/workers/ServiceWorker.h
+++ b/dom/workers/ServiceWorker.h
@@ -52,6 +52,11 @@ public:
     aURL = mURL;
   }
 
+  void
+  PostMessage(JSContext* aCx, JS::Handle<JS::Value> aMessage,
+              const Optional<Sequence<JS::Value>>& aTransferable,
+              ErrorResult& aRv);
+
   WorkerPrivate*
   GetWorkerPrivate() const;