diff --git a/widget/windows/WinIMEHandler.cpp b/widget/windows/WinIMEHandler.cpp
index 40b7ad5e3b1..ed4e8c6ce10 100644
--- a/widget/windows/WinIMEHandler.cpp
+++ b/widget/windows/WinIMEHandler.cpp
@@ -289,7 +289,7 @@ IMEHandler::SetInputContext(nsWindow* aWindow,
   if (sIsInTSFMode) {
     nsTextStore::SetInputContext(aWindow, aInputContext, aAction);
     if (IsTSFAvailable()) {
-      aInputContext.mNativeIMEContext = nsTextStore::GetTextStore();
+      aInputContext.mNativeIMEContext = nsTextStore::GetThreadManager();
       if (sIsIMMEnabled) {
         // Associate IME context for IMM-IMEs.
         AssociateIMEContext(aWindow, enable);
@@ -354,7 +354,7 @@ IMEHandler::InitInputContext(nsWindow* aWindow, InputContext& aInputContext)
     nsTextStore::SetInputContext(aWindow, aInputContext,
       InputContextAction(InputContextAction::CAUSE_UNKNOWN,
                          InputContextAction::GOT_FOCUS));
-    aInputContext.mNativeIMEContext = nsTextStore::GetTextStore();
+    aInputContext.mNativeIMEContext = nsTextStore::GetThreadManager();
     MOZ_ASSERT(aInputContext.mNativeIMEContext);
     // IME context isn't necessary in pure TSF mode.
     if (!sIsIMMEnabled) {
diff --git a/widget/windows/nsTextStore.cpp b/widget/windows/nsTextStore.cpp
index 3902b1619e3..97e94068718 100644
--- a/widget/windows/nsTextStore.cpp
+++ b/widget/windows/nsTextStore.cpp
@@ -3669,7 +3669,7 @@ nsTextStore::OnFocusChange(bool aGotFocus,
           sTsfThreadMgr, sEnabledTextStore));
 
   // no change notifications if TSF is disabled
-  NS_ENSURE_TRUE(sTsfThreadMgr && sEnabledTextStore, NS_ERROR_NOT_AVAILABLE);
+  NS_ENSURE_TRUE(IsInTSFMode(), NS_ERROR_NOT_AVAILABLE);
 
   nsRefPtr<ITfDocumentMgr> prevFocusedDocumentMgr;
   if (aGotFocus && aIMEState.IsEditable()) {
@@ -4208,12 +4208,17 @@ nsTextStore::SetInputContext(nsWindowBase* aWidget,
   PR_LOG(sTextStoreLog, PR_LOG_DEBUG,
          ("TSF: nsTextStore::SetInputContext(aWidget=%p, "
           "aContext.mIMEState.mEnabled=%s, aAction.mFocusChange=%s), "
-          "ThinksHavingFocus()=%s",
+          "sEnabledTextStore=0x%p, ThinksHavingFocus()=%s",
           aWidget, GetIMEEnabledName(aContext.mIMEState.mEnabled),
-          GetFocusChangeName(aAction.mFocusChange),
+          GetFocusChangeName(aAction.mFocusChange), sEnabledTextStore,
           GetBoolName(ThinksHavingFocus())));
 
-  NS_ENSURE_TRUE_VOID(sEnabledTextStore);
+  NS_ENSURE_TRUE_VOID(IsInTSFMode());
+
+  if (!sEnabledTextStore) {
+    return;
+  }
+
   sEnabledTextStore->SetInputScope(aContext.mHTMLInputType);
 
   if (aAction.mFocusChange != InputContextAction::FOCUS_NOT_CHANGED) {
diff --git a/widget/windows/nsTextStore.h b/widget/windows/nsTextStore.h
index e429c92801d..a57b95e6ee8 100644
--- a/widget/windows/nsTextStore.h
+++ b/widget/windows/nsTextStore.h
@@ -134,8 +134,10 @@ public:
 
   static void     CommitComposition(bool aDiscard)
   {
-    NS_ENSURE_TRUE_VOID(sEnabledTextStore);
-    sEnabledTextStore->CommitCompositionInternal(aDiscard);
+    NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
+    if (sEnabledTextStore) {
+      sEnabledTextStore->CommitCompositionInternal(aDiscard);
+    }
   }
 
   static void SetInputContext(nsWindowBase* aWidget,
@@ -147,28 +149,30 @@ public:
                                 const IMEState& aIMEState);
   static nsresult OnTextChange(const IMENotification& aIMENotification)
   {
-    NS_ENSURE_TRUE(sEnabledTextStore, NS_ERROR_NOT_AVAILABLE);
-    return sEnabledTextStore->OnTextChangeInternal(aIMENotification);
+    NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
+    return sEnabledTextStore ?
+      sEnabledTextStore->OnTextChangeInternal(aIMENotification) : NS_OK;
   }
 
   static nsresult OnSelectionChange(void)
   {
-    NS_ENSURE_TRUE(sEnabledTextStore, NS_ERROR_NOT_AVAILABLE);
-    return sEnabledTextStore->OnSelectionChangeInternal();
+    NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
+    return sEnabledTextStore ?
+      sEnabledTextStore->OnSelectionChangeInternal() : NS_OK;
   }
 
   static nsresult OnLayoutChange()
   {
-    NS_ENSURE_TRUE(sEnabledTextStore, NS_ERROR_NOT_AVAILABLE);
-    return sEnabledTextStore->OnLayoutChangeInternal();
+    NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
+    return sEnabledTextStore ?
+      sEnabledTextStore->OnLayoutChangeInternal() : NS_OK;
   }
 
   static nsresult OnMouseButtonEvent(const IMENotification& aIMENotification)
   {
-    if (NS_WARN_IF(!sEnabledTextStore)) {
-      return NS_ERROR_NOT_AVAILABLE;
-    }
-    return sEnabledTextStore->OnMouseButtonEventInternal(aIMENotification);
+    NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
+    return sEnabledTextStore ?
+      sEnabledTextStore->OnMouseButtonEventInternal(aIMENotification) : NS_OK;
   }
 
   static nsIMEUpdatePreference GetIMEUpdatePreference();
@@ -195,32 +199,32 @@ public:
     return sMessagePump;
   }
 
-  static void*    GetTextStore()
+  static void* GetThreadManager()
   {
-    return static_cast<void*>(sEnabledTextStore);
+    return static_cast<void*>(sTsfThreadMgr);
   }
 
-  static bool     ThinksHavingFocus()
+  static bool ThinksHavingFocus()
   {
     return (sEnabledTextStore && sEnabledTextStore->mContext);
   }
 
-  static bool     IsInTSFMode()
+  static bool IsInTSFMode()
   {
     return sTsfThreadMgr != nullptr;
   }
 
-  static bool     IsComposing()
+  static bool IsComposing()
   {
     return (sEnabledTextStore && sEnabledTextStore->mComposition.IsComposing());
   }
 
-  static bool     IsComposingOn(nsWindowBase* aWidget)
+  static bool IsComposingOn(nsWindowBase* aWidget)
   {
     return (IsComposing() && sEnabledTextStore->mWidget == aWidget);
   }
 
-  static bool     IsIMM_IME()
+  static bool IsIMM_IME()
   {
     if (!sEnabledTextStore ||
         !sEnabledTextStore->EnsureInitActiveTIPKeyboard()) {
@@ -229,7 +233,7 @@ public:
     return sEnabledTextStore->mIsIMM_IME;
   }
 
-  static bool     IsIMM_IME(HKL aHKL)
+  static bool IsIMM_IME(HKL aHKL)
   {
      return (::ImmGetIMEFileNameW(aHKL, nullptr, 0) > 0);
   }
diff --git a/widget/windows/winrt/MetroWidget.cpp b/widget/windows/winrt/MetroWidget.cpp
index e1b35e07adf..36dcefa2b73 100644
--- a/widget/windows/winrt/MetroWidget.cpp
+++ b/widget/windows/winrt/MetroWidget.cpp
@@ -1542,6 +1542,7 @@ NS_IMETHODIMP_(void)
 MetroWidget::SetInputContext(const InputContext& aContext,
                              const InputContextAction& aAction)
 {
+  // XXX This should set mInputContext.mNativeIMEContext properly
   mInputContext = aContext;
   nsTextStore::SetInputContext(this, mInputContext, aAction);
   bool enable = (mInputContext.mIMEState.mEnabled == IMEState::ENABLED ||