diff --git a/dom/events/CommandEvent.cpp b/dom/events/CommandEvent.cpp
index ddad7ed9a3b0..8742526aebeb 100644
--- a/dom/events/CommandEvent.cpp
+++ b/dom/events/CommandEvent.cpp
@@ -15,8 +15,7 @@ CommandEvent::CommandEvent(EventTarget* aOwner,
                            nsPresContext* aPresContext,
                            WidgetCommandEvent* aEvent)
   : Event(aOwner, aPresContext,
-          aEvent ? aEvent :
-                   new WidgetCommandEvent(false, nullptr, nullptr, nullptr))
+          aEvent ? aEvent : new WidgetCommandEvent())
 {
   mEvent->mTime = PR_Now();
   if (aEvent) {
diff --git a/widget/MiscEvents.h b/widget/MiscEvents.h
index 7a7fc8349701..7817492c01b2 100644
--- a/widget/MiscEvents.h
+++ b/widget/MiscEvents.h
@@ -11,6 +11,7 @@
 #include "mozilla/BasicEvents.h"
 #include "nsCOMPtr.h"
 #include "nsAtom.h"
+#include "nsGkAtoms.h"
 #include "nsITransferable.h"
 
 namespace mozilla {
@@ -106,6 +107,7 @@ class WidgetCommandEvent : public WidgetGUIEvent
 public:
   virtual WidgetCommandEvent* AsCommandEvent() override { return this; }
 
+protected:
   WidgetCommandEvent(bool aIsTrusted, nsAtom* aEventType,
                      nsAtom* aCommand, nsIWidget* aWidget)
     : WidgetGUIEvent(aIsTrusted, eUnidentifiedEvent, aWidget,
@@ -115,6 +117,25 @@ public:
     mSpecifiedEventType = aEventType;
   }
 
+public:
+  /**
+   * Constructor to initialize an app command.  This is the only case to
+   * initialize this class as a command in C++ stack.
+   */
+  WidgetCommandEvent(bool aIsTrusted, nsAtom* aCommand, nsIWidget* aWidget)
+    : WidgetCommandEvent(aIsTrusted, nsGkAtoms::onAppCommand,
+                         aCommand, aWidget)
+  {
+  }
+
+  /**
+   * Constructor to initialize as internal event of dom::CommandEvent.
+   */
+  WidgetCommandEvent()
+    : WidgetCommandEvent(false, nullptr, nullptr, nullptr)
+  {
+  }
+
   virtual WidgetEvent* Duplicate() const override
   {
     MOZ_ASSERT(mClass == eCommandEventClass,
diff --git a/widget/gtk/nsWindow.cpp b/widget/gtk/nsWindow.cpp
index cf8b9f9f0fc3..416db73a7401 100644
--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -2933,8 +2933,8 @@ bool
 nsWindow::DispatchCommandEvent(nsAtom* aCommand)
 {
     nsEventStatus status;
-    WidgetCommandEvent event(true, nsGkAtoms::onAppCommand, aCommand, this);
-    DispatchEvent(&event, status);
+    WidgetCommandEvent appCommandEvent(true, aCommand, this);
+    DispatchEvent(&appCommandEvent, status);
     return TRUE;
 }
 
diff --git a/widget/windows/KeyboardLayout.cpp b/widget/windows/KeyboardLayout.cpp
index 69e90feb289a..efe869113e4b 100644
--- a/widget/windows/KeyboardLayout.cpp
+++ b/widget/windows/KeyboardLayout.cpp
@@ -2146,16 +2146,17 @@ NativeKey::DispatchCommandEvent(uint32_t aEventCommand) const
          "event", this));
       return false;
   }
-  WidgetCommandEvent commandEvent(true, nsGkAtoms::onAppCommand,
-                                  command, mWidget);
+  WidgetCommandEvent appCommandEvent(true, command, mWidget);
 
-  mWidget->InitEvent(commandEvent);
+  mWidget->InitEvent(appCommandEvent);
   MOZ_LOG(sNativeKeyLogger, LogLevel::Info,
-    ("%p   NativeKey::DispatchCommandEvent(), dispatching %s command event...",
+    ("%p   NativeKey::DispatchCommandEvent(), dispatching "
+     "%s app command event...",
      this, nsAtomCString(command).get()));
-  bool ok = mWidget->DispatchWindowEvent(&commandEvent) || mWidget->Destroyed();
+  bool ok =
+    mWidget->DispatchWindowEvent(&appCommandEvent) || mWidget->Destroyed();
   MOZ_LOG(sNativeKeyLogger, LogLevel::Info,
-    ("%p   NativeKey::DispatchCommandEvent(), dispatched command event, "
+    ("%p   NativeKey::DispatchCommandEvent(), dispatched app command event, "
      "result=%s, mWidget->Destroyed()=%s",
      this, GetBoolName(ok), GetBoolName(mWidget->Destroyed())));
   return ok;
diff --git a/widget/windows/WinMouseScrollHandler.cpp b/widget/windows/WinMouseScrollHandler.cpp
index 104756e261e8..13b29fb03ec8 100644
--- a/widget/windows/WinMouseScrollHandler.cpp
+++ b/widget/windows/WinMouseScrollHandler.cpp
@@ -1415,10 +1415,10 @@ MouseScrollHandler::Device::Elantech::HandleKeyMessage(nsWindowBase* aWidget,
          "%s command event",
          aWParam == VK_NEXT ? "Forward" : "Back"));
 
-      WidgetCommandEvent commandEvent(true, nsGkAtoms::onAppCommand,
+      WidgetCommandEvent appCommandEvent(true,
         (aWParam == VK_NEXT) ? nsGkAtoms::Forward : nsGkAtoms::Back, aWidget);
-      InitEvent(aWidget, commandEvent);
-      aWidget->DispatchWindowEvent(&commandEvent);
+      InitEvent(aWidget, appCommandEvent);
+      aWidget->DispatchWindowEvent(&appCommandEvent);
     }
     else {
       MOZ_LOG(gMouseScrollLog, LogLevel::Info,