diff --git a/dom/events/CommandEvent.cpp b/dom/events/CommandEvent.cpp
index e548c89e0b73..dc6ee029fb64 100644
--- a/dom/events/CommandEvent.cpp
+++ b/dom/events/CommandEvent.cpp
@@ -36,7 +36,7 @@ NS_IMPL_RELEASE_INHERITED(CommandEvent, Event)
 NS_IMETHODIMP
 CommandEvent::GetCommand(nsAString& aCommand)
 {
-  nsIAtom* command = mEvent->AsCommandEvent()->command;
+  nsIAtom* command = mEvent->AsCommandEvent()->mCommand;
   if (command) {
     command->ToString(aCommand);
   } else {
@@ -53,7 +53,7 @@ CommandEvent::InitCommandEvent(const nsAString& aTypeArg,
 {
   Event::InitEvent(aTypeArg, aCanBubbleArg, aCancelableArg);
 
-  mEvent->AsCommandEvent()->command = NS_Atomize(aCommand);
+  mEvent->AsCommandEvent()->mCommand = NS_Atomize(aCommand);
   return NS_OK;
 }
 
diff --git a/widget/MiscEvents.h b/widget/MiscEvents.h
index 6066fc0aa47d..2ef581d79529 100644
--- a/widget/MiscEvents.h
+++ b/widget/MiscEvents.h
@@ -110,7 +110,7 @@ public:
                      nsIAtom* aCommand, nsIWidget* aWidget)
     : WidgetGUIEvent(aIsTrusted, eUnidentifiedEvent, aWidget,
                      eCommandEventClass)
-    , command(aCommand)
+    , mCommand(aCommand)
   {
     mSpecifiedEventType = aEventType;
   }
@@ -121,13 +121,13 @@ public:
                "Duplicate() must be overridden by sub class");
     // Not copying widget, it is a weak reference.
     WidgetCommandEvent* result =
-      new WidgetCommandEvent(false, mSpecifiedEventType, command, nullptr);
+      new WidgetCommandEvent(false, mSpecifiedEventType, mCommand, nullptr);
     result->AssignCommandEventData(*this, true);
     result->mFlags = mFlags;
     return result;
   }
 
-  nsCOMPtr<nsIAtom> command;
+  nsCOMPtr<nsIAtom> mCommand;
 
   // XXX Not tested by test_assign_event_data.html
   void AssignCommandEventData(const WidgetCommandEvent& aEvent,
@@ -135,7 +135,7 @@ public:
   {
     AssignGUIEventData(aEvent, aCopyTargets);
 
-    // command must have been initialized with the constructor.
+    // mCommand must have been initialized with the constructor.
   }
 };