--- a/widget/windows/TSFTextStore.cpp
+++ b/widget/windows/TSFTextStore.cpp
@@ -4521,66 +4521,66 @@ TSFTextStore::OnFocusChange(bool aGotFoc
 // static
 bool
 TSFTextStore::CreateAndSetFocus(nsWindowBase* aFocusedWidget,
                                 const InputContext& aContext)
 {
   // TSF might do something which causes that we need to access static methods
   // of TSFTextStore.  At that time, sEnabledTextStore may be necessary.
   // So, we should set sEnabledTextStore directly.
-  sEnabledTextStore = new TSFTextStore();
-  if (NS_WARN_IF(!sEnabledTextStore->Init(aFocusedWidget))) {
+  RefPtr<TSFTextStore> textStore = new TSFTextStore();
+  sEnabledTextStore = textStore;
+  if (NS_WARN_IF(!textStore->Init(aFocusedWidget))) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
            ("TSF:   TSFTextStore::CreateAndSetFocus() FAILED due to "
             "TSFTextStore::Init() failure"));
     return false;
   }
-  if (NS_WARN_IF(!sEnabledTextStore->mDocumentMgr)) {
+  if (NS_WARN_IF(!textStore->mDocumentMgr)) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
            ("TSF:   TSFTextStore::CreateAndSetFocus() FAILED due to "
             "invalid TSFTextStore::mDocumentMgr"));
     return false;
   }
   if (aContext.mIMEState.mEnabled == IMEState::PASSWORD) {
-    MarkContextAsKeyboardDisabled(sEnabledTextStore->mContext);
+    MarkContextAsKeyboardDisabled(textStore->mContext);
     RefPtr<ITfContext> topContext;
-    sEnabledTextStore->mDocumentMgr->GetTop(getter_AddRefs(topContext));
-    if (topContext && topContext != sEnabledTextStore->mContext) {
+    textStore->mDocumentMgr->GetTop(getter_AddRefs(topContext));
+    if (topContext && topContext != textStore->mContext) {
       MarkContextAsKeyboardDisabled(topContext);
     }
   }
-  HRESULT hr = sThreadMgr->SetFocus(sEnabledTextStore->mDocumentMgr);
+  HRESULT hr = sThreadMgr->SetFocus(textStore->mDocumentMgr);
   if (NS_WARN_IF(FAILED(hr))) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
            ("TSF:   TSFTextStore::CreateAndSetFocus() FAILED due to "
             "ITfTheadMgr::SetFocus() failure"));
     return false;
   }
   // Use AssociateFocus() for ensuring that any native focus event
   // never steal focus from our documentMgr.
   RefPtr<ITfDocumentMgr> prevFocusedDocumentMgr;
   hr = sThreadMgr->AssociateFocus(aFocusedWidget->GetWindowHandle(),
-                                  sEnabledTextStore->mDocumentMgr,
+                                  textStore->mDocumentMgr,
                                   getter_AddRefs(prevFocusedDocumentMgr));
   if (NS_WARN_IF(FAILED(hr))) {
     MOZ_LOG(sTextStoreLog, LogLevel::Error,
            ("TSF:   TSFTextStore::CreateAndSetFocus() FAILED due to "
             "ITfTheadMgr::AssociateFocus() failure"));
     return false;
   }
-  sEnabledTextStore->SetInputScope(aContext.mHTMLInputType,
-                                   aContext.mHTMLInputInputmode);
-
-  if (sEnabledTextStore->mSink) {
+  textStore->SetInputScope(aContext.mHTMLInputType,
+                           aContext.mHTMLInputInputmode);
+
+  if (textStore->mSink) {
     MOZ_LOG(sTextStoreLog, LogLevel::Info,
       ("TSF:   TSFTextStore::CreateAndSetFocus(), calling "
        "ITextStoreACPSink::OnLayoutChange(TS_LC_CREATE) for 0x%p...",
-       sEnabledTextStore.get()));
-    sEnabledTextStore->mSink->OnLayoutChange(TS_LC_CREATE,
-                                             TEXTSTORE_DEFAULT_VIEW);
+       textStore.get()));
+    textStore->mSink->OnLayoutChange(TS_LC_CREATE, TEXTSTORE_DEFAULT_VIEW);
   }
   return true;
 }
 
 // static
 nsIMEUpdatePreference
 TSFTextStore::GetIMEUpdatePreference()
 {
@@ -5299,18 +5299,19 @@ TSFTextStore::SetInputContext(nsWindowBa
           aWidget, GetIMEEnabledName(aContext.mIMEState.mEnabled),
           GetFocusChangeName(aAction.mFocusChange), sEnabledTextStore.get(),
           GetBoolName(ThinksHavingFocus())));
 
   NS_ENSURE_TRUE_VOID(IsInTSFMode());
 
   if (aAction.mFocusChange != InputContextAction::FOCUS_NOT_CHANGED) {
     if (sEnabledTextStore) {
-      sEnabledTextStore->SetInputScope(aContext.mHTMLInputType,
-                                       aContext.mHTMLInputInputmode);
+      RefPtr<TSFTextStore> textStore = sEnabledTextStore;
+      textStore->SetInputScope(aContext.mHTMLInputType,
+                               aContext.mHTMLInputInputmode);
     }
     return;
   }
 
   // If focus isn't actually changed but the enabled state is changed,
   // emulate the focus move.
   if (!ThinksHavingFocus() && aContext.mIMEState.IsEditable()) {
     OnFocusChange(true, aWidget, aContext);
@@ -5641,18 +5642,19 @@ TSFTextStore::ProcessMessage(nsWindowBas
       // When an modal dialog such as a file picker is open, composition
       // should be committed because IME might be used on it.
       if (!IsComposingOn(aWindow)) {
         break;
       }
       CommitComposition(false);
       break;
     case MOZ_WM_NOTIY_TSF_OF_LAYOUT_CHANGE: {
-      TSFTextStore* textStore = reinterpret_cast<TSFTextStore*>(aWParam);
-      if (textStore == sEnabledTextStore) {
+      TSFTextStore* maybeTextStore = reinterpret_cast<TSFTextStore*>(aWParam);
+      if (maybeTextStore == sEnabledTextStore) {
+        RefPtr<TSFTextStore> textStore(maybeTextStore);
         textStore->NotifyTSFOfLayoutChangeAgain();
       }
       break;
     }
   }
 }
 
 // static

--- a/widget/windows/TSFTextStore.h
+++ b/widget/windows/TSFTextStore.h
@@ -111,61 +111,78 @@ public:
 
 
   static void     SetIMEOpenState(bool);
   static bool     GetIMEOpenState(void);
 
   static void     CommitComposition(bool aDiscard)
   {
     NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
-    if (sEnabledTextStore) {
-      sEnabledTextStore->CommitCompositionInternal(aDiscard);
+    if (!sEnabledTextStore) {
+      return;
     }
+    RefPtr<TSFTextStore> textStore = sEnabledTextStore;
+    textStore->CommitCompositionInternal(aDiscard);
   }
 
   static void SetInputContext(nsWindowBase* aWidget,
                               const InputContext& aContext,
                               const InputContextAction& aAction);
 
   static nsresult OnFocusChange(bool aGotFocus,
                                 nsWindowBase* aFocusedWidget,
                                 const InputContext& aContext);
   static nsresult OnTextChange(const IMENotification& aIMENotification)
   {
     NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
-    return sEnabledTextStore ?
-      sEnabledTextStore->OnTextChangeInternal(aIMENotification) : NS_OK;
+    if (!sEnabledTextStore) {
+      return NS_OK;
+    }
+    RefPtr<TSFTextStore> textStore = sEnabledTextStore;
+    return textStore->OnTextChangeInternal(aIMENotification);
   }
 
   static nsresult OnSelectionChange(const IMENotification& aIMENotification)
   {
     NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
-    return sEnabledTextStore ?
-      sEnabledTextStore->OnSelectionChangeInternal(aIMENotification) : NS_OK;
+    if (!sEnabledTextStore) {
+      return NS_OK;
+    }
+    RefPtr<TSFTextStore> textStore = sEnabledTextStore;
+    return textStore->OnSelectionChangeInternal(aIMENotification);
   }
 
   static nsresult OnLayoutChange()
   {
     NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
-    return sEnabledTextStore ?
-      sEnabledTextStore->OnLayoutChangeInternal() : NS_OK;
+    if (!sEnabledTextStore) {
+      return NS_OK;
+    }
+    RefPtr<TSFTextStore> textStore = sEnabledTextStore;
+    return textStore->OnLayoutChangeInternal();
   }
 
   static nsresult OnUpdateComposition()
   {
     NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
-    return sEnabledTextStore ?
-      sEnabledTextStore->OnUpdateCompositionInternal() : NS_OK;
+    if (!sEnabledTextStore) {
+      return NS_OK;
+    }
+    RefPtr<TSFTextStore> textStore = sEnabledTextStore;
+    return textStore->OnUpdateCompositionInternal();
   }
 
   static nsresult OnMouseButtonEvent(const IMENotification& aIMENotification)
   {
     NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
-    return sEnabledTextStore ?
-      sEnabledTextStore->OnMouseButtonEventInternal(aIMENotification) : NS_OK;
+    if (!sEnabledTextStore) {
+      return NS_OK;
+    }
+    RefPtr<TSFTextStore> textStore = sEnabledTextStore;
+    return textStore->OnMouseButtonEventInternal(aIMENotification);
   }
 
   static nsIMEUpdatePreference GetIMEUpdatePreference();
 
   // Returns the address of the pointer so that the TSF automatic test can
   // replace the system object with a custom implementation for testing.
   // XXX TSF doesn't work now.  Should we remove it?
   static void* GetNativeData(uint32_t aDataType)