diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index 554719e2d92..f537d84f866 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -1395,7 +1395,6 @@ nsGlobalWindow::CleanUp(bool aIgnoreModalDialog)
 
   mInnerWindowHolder = nullptr;
   mArguments = nullptr;
-  mArgumentsLast = nullptr;
   mArgumentsOrigin = nullptr;
 
   CleanupCachedXBLHandlers(this);
@@ -1624,7 +1623,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(nsGlobalWindow)
 
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mControllers)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mArguments)
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mArgumentsLast)
 
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mPerformance)
 
@@ -1671,7 +1669,6 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsGlobalWindow)
 
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mControllers)
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mArguments)
-  NS_IMPL_CYCLE_COLLECTION_UNLINK(mArgumentsLast)
 
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mPerformance)
 
@@ -2738,7 +2735,6 @@ nsGlobalWindow::DetachFromDocShell()
     // We got no new document after someone called
     // SetArguments(), drop our reference to the arguments.
     mArguments = nullptr;
-    mArgumentsLast = nullptr;
     mArgumentsOrigin = nullptr;
   }
 
@@ -3155,9 +3151,7 @@ nsGlobalWindow::SetArguments(nsIArray *aArguments, nsIPrincipal *aOrigin)
 
   nsGlobalWindow *currentInner = GetCurrentInnerWindowInternal();
 
-  if (!mIsModalContentWindow) {
-    mArgumentsLast = aArguments;
-  } else if (currentInner) {
+  if (mIsModalContentWindow && currentInner) {
     // SetArguments() is being called on a modal content window that
     // already has an inner window. This can happen when loading
     // javascript: URIs as modal content dialogs. In this case, we'll
diff --git a/dom/base/nsGlobalWindow.h b/dom/base/nsGlobalWindow.h
index 39f63c7f67b..f49ccbab528 100644
--- a/dom/base/nsGlobalWindow.h
+++ b/dom/base/nsGlobalWindow.h
@@ -1114,7 +1114,6 @@ protected:
   nsWeakPtr                     mOpener;
   nsCOMPtr<nsIControllers>      mControllers;
   nsCOMPtr<nsIArray>            mArguments;
-  nsCOMPtr<nsIArray>            mArgumentsLast;
   nsCOMPtr<nsIPrincipal>        mArgumentsOrigin;
   nsRefPtr<Navigator>           mNavigator;
   nsRefPtr<nsScreen>            mScreen;