diff --git a/dom/ipc/ContentChild.cpp b/dom/ipc/ContentChild.cpp
index e49d1a12baa..18fa5637c4c 100644
--- a/dom/ipc/ContentChild.cpp
+++ b/dom/ipc/ContentChild.cpp
@@ -77,6 +77,7 @@
 
 #if defined(MOZ_WIDGET_GONK)
 #include "nsVolume.h"
+#include "nsVolumeService.h"
 #endif
 
 #ifdef XP_WIN
@@ -1186,9 +1187,10 @@ ContentChild::RecvFileSystemUpdate(const nsString& aFsName,
     nsRefPtr<nsVolume> volume = new nsVolume(aFsName, aVolumeName, aState,
                                              aMountGeneration);
 
-    nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
-    NS_ConvertUTF8toUTF16 stateStr(volume->StateStr());
-    obs->NotifyObservers(volume, NS_VOLUME_STATE_CHANGED, stateStr.get());
+    nsRefPtr<nsVolumeService> vs = nsVolumeService::GetSingleton();
+    if (vs) {
+        vs->UpdateVolume(volume);
+    }
 #else
     // Remove warnings about unused arguments
     unused << aFsName;
diff --git a/dom/system/gonk/moz.build b/dom/system/gonk/moz.build
index 7fee24e8954..b1e1398a7f7 100644
--- a/dom/system/gonk/moz.build
+++ b/dom/system/gonk/moz.build
@@ -39,6 +39,7 @@ if CONFIG['MOZ_WIDGET_TOOLKIT'] == 'gonk':
     EXPORTS += [
         'GonkGPSGeolocationProvider.h',
         'nsVolume.h',
+        'nsVolumeService.h',
     ]
 
 if CONFIG['ENABLE_TESTS']:
diff --git a/dom/system/gonk/nsVolumeService.cpp b/dom/system/gonk/nsVolumeService.cpp
index d34163b57cf..51209c18c89 100644
--- a/dom/system/gonk/nsVolumeService.cpp
+++ b/dom/system/gonk/nsVolumeService.cpp
@@ -66,8 +66,6 @@ nsVolumeService::Shutdown()
     return;
   }
   if (XRE_GetProcessType() != GeckoProcessType_Default) {
-    nsCOMPtr<nsIObserverService> obs = GetObserverService();
-    obs->RemoveObserver(sSingleton.get(), NS_VOLUME_STATE_CHANGED);
     sSingleton = nullptr;
     return;
   }
@@ -91,10 +89,6 @@ nsVolumeService::nsVolumeService()
   sSingleton = this;
 
   if (XRE_GetProcessType() != GeckoProcessType_Default) {
-    // For child processes, we keep a cache of the volume state.
-    nsCOMPtr<nsIObserverService> obs = GetObserverService();
-    obs->AddObserver(this, NS_VOLUME_STATE_CHANGED, false /*weak*/);
-
     // Request the initial state for all volumes.
     ContentChild::GetSingleton()->SendBroadcastVolume(NS_LITERAL_STRING(""));
     return;
@@ -347,21 +341,6 @@ nsVolumeService::CreateOrFindVolumeByName(const nsAString& aName)
   return vol.forget();
 }
 
-NS_IMETHODIMP
-nsVolumeService::Observe(nsISupports* aSubject, const char* aTopic, const PRUnichar* aData)
-{
-  if (strcmp(aTopic, NS_VOLUME_STATE_CHANGED) != 0) {
-    return NS_OK;
-  }
-  MOZ_ASSERT(XRE_GetProcessType() != GeckoProcessType_Default);
-  nsCOMPtr<nsIVolume> vol = do_QueryInterface(aSubject);
-  if (!vol) {
-    return NS_OK;
-  }
-  UpdateVolume(vol);
-  return NS_OK;
-}
-
 void
 nsVolumeService::UpdateVolume(nsIVolume* aVolume)
 {
@@ -375,10 +354,6 @@ nsVolumeService::UpdateVolume(nsIVolume* aVolume)
     return;
   }
   vol->Set(aVolume);
-  if (XRE_GetProcessType() != GeckoProcessType_Default) {
-    // Only the parent broadcasts the state changes
-    return;
-  }
   nsCOMPtr<nsIObserverService> obs = GetObserverService();
   if (!obs) {
     return;
diff --git a/dom/system/gonk/nsVolumeService.h b/dom/system/gonk/nsVolumeService.h
index 5cfaed1f5b7..34eb710cf0a 100644
--- a/dom/system/gonk/nsVolumeService.h
+++ b/dom/system/gonk/nsVolumeService.h
@@ -10,16 +10,15 @@
 #include "mozilla/StaticPtr.h"
 #include "nsCOMPtr.h"
 #include "nsIDOMWakeLockListener.h"
-#include "nsIObserver.h"
 #include "nsIVolume.h"
 #include "nsIVolumeService.h"
 #include "nsVolume.h"
-#include "Volume.h"
 
 namespace mozilla {
 namespace system {
 
 class WakeLockCallback;
+class Volume;
 
 /***************************************************************************
 * The nsVolumeData class encapsulates the data that is updated/maintained
@@ -28,12 +27,10 @@ class WakeLockCallback;
 */
 
 class nsVolumeService MOZ_FINAL : public nsIVolumeService,
-                                  public nsIObserver,
                                   public nsIDOMMozWakeLockListener
 {
 public:
   NS_DECL_ISUPPORTS
-  NS_DECL_NSIOBSERVER
   NS_DECL_NSIVOLUMESERVICE
   NS_DECL_NSIDOMMOZWAKELOCKLISTENER