diff --git a/widget/windows/WinIMEHandler.cpp b/widget/windows/WinIMEHandler.cpp
index 6e15d42612a4..c0e9b87b650a 100644
--- a/widget/windows/WinIMEHandler.cpp
+++ b/widget/windows/WinIMEHandler.cpp
@@ -11,6 +11,7 @@
 #endif // #ifdef NS_ENABLE_TSF
 
 #include "nsWindow.h"
+#include "WinUtils.h"
 
 namespace mozilla {
 namespace widget {
@@ -98,6 +99,18 @@ IMEHandler::IsIMEEnabled(IMEState::Enabled aIMEState)
           aIMEState == mozilla::widget::IMEState::PLUGIN);
 }
 
+// static
+bool
+IMEHandler::ProcessRawKeyMessage(const MSG& aMsg)
+{
+#ifdef NS_ENABLE_TSF
+  if (IsTSFAvailable()) {
+    return nsTextStore::ProcessRawKeyMessage(aMsg);
+  }
+#endif // #ifdef NS_ENABLE_TSF
+  return false; // noting to do in IMM mode.
+}
+
 // static
 bool
 IMEHandler::ProcessMessage(nsWindow* aWindow, UINT aMessage,
@@ -369,13 +382,13 @@ IMEHandler::IsDoingKakuteiUndo(HWND aWnd)
   // https://bugzilla.mozilla.gr.jp/show_bug.cgi?id=2885 (written in Japanese)
   // https://bugzilla.mozilla.org/show_bug.cgi?id=194559 (written in English)
   MSG startCompositionMsg, compositionMsg, charMsg;
-  return ::PeekMessageW(&startCompositionMsg, aWnd,
-                        WM_IME_STARTCOMPOSITION, WM_IME_STARTCOMPOSITION,
-                        PM_NOREMOVE | PM_NOYIELD) &&
-         ::PeekMessageW(&compositionMsg, aWnd, WM_IME_COMPOSITION,
-                        WM_IME_COMPOSITION, PM_NOREMOVE | PM_NOYIELD) &&
-         ::PeekMessageW(&charMsg, aWnd, WM_CHAR, WM_CHAR,
-                        PM_NOREMOVE | PM_NOYIELD) &&
+  return WinUtils::PeekMessage(&startCompositionMsg, aWnd,
+                               WM_IME_STARTCOMPOSITION, WM_IME_STARTCOMPOSITION,
+                               PM_NOREMOVE | PM_NOYIELD) &&
+         WinUtils::PeekMessage(&compositionMsg, aWnd, WM_IME_COMPOSITION,
+                               WM_IME_COMPOSITION, PM_NOREMOVE | PM_NOYIELD) &&
+         WinUtils::PeekMessage(&charMsg, aWnd, WM_CHAR, WM_CHAR,
+                               PM_NOREMOVE | PM_NOYIELD) &&
          startCompositionMsg.wParam == 0x0 &&
          startCompositionMsg.lParam == 0x0 &&
          compositionMsg.wParam == 0x0 &&
diff --git a/widget/windows/WinIMEHandler.h b/widget/windows/WinIMEHandler.h
index b9b219e43d47..0f371e3b456a 100644
--- a/widget/windows/WinIMEHandler.h
+++ b/widget/windows/WinIMEHandler.h
@@ -48,6 +48,13 @@ public:
   static bool IsIMEEnabled(const InputContext& aInputContext);
   static bool IsIMEEnabled(IMEState::Enabled aIMEState);
 
+  /**
+   * ProcessRawKeyMessage() message is called before calling TranslateMessage()
+   * and DispatchMessage().  If this returns true, the message is consumed.
+   * Then, caller must not perform TranslateMessage() nor DispatchMessage().
+   */
+  static bool ProcessRawKeyMessage(const MSG& aMsg);
+
   /**
    * When the message is not needed to handle anymore by the caller, this
    * returns true.  Otherwise, false.
diff --git a/widget/windows/WinUtils.cpp b/widget/windows/WinUtils.cpp
index 472449ebc87c..98ac5009ae2d 100644
--- a/widget/windows/WinUtils.cpp
+++ b/widget/windows/WinUtils.cpp
@@ -27,6 +27,11 @@
 #include "nsIObserver.h"
 #include "imgIEncoder.h"
 
+#ifdef NS_ENABLE_TSF
+#include <textstor.h>
+#include "nsTextStore.h"
+#endif // #ifdef NS_ENABLE_TSF
+
 namespace mozilla {
 namespace widget {
 
@@ -68,6 +73,42 @@ WinUtils::GetWindowsVersion()
   return static_cast<WinVersion>(version);
 }
 
+/* static */
+bool
+WinUtils::PeekMessage(LPMSG aMsg, HWND aWnd, UINT aFirstMessage,
+                      UINT aLastMessage, UINT aOption)
+{
+#ifdef NS_ENABLE_TSF
+  ITfMessagePump* msgPump = nsTextStore::GetMessagePump();
+  if (msgPump) {
+    BOOL ret = FALSE;
+    HRESULT hr = msgPump->PeekMessageW(aMsg, aWnd, aFirstMessage, aLastMessage,
+                                       aOption, &ret);
+    NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+    return ret;
+  }
+#endif // #ifdef NS_ENABLE_TSF
+  return ::PeekMessageW(aMsg, aWnd, aFirstMessage, aLastMessage, aOption);
+}
+
+/* static */
+bool
+WinUtils::GetMessage(LPMSG aMsg, HWND aWnd, UINT aFirstMessage,
+                     UINT aLastMessage)
+{
+#ifdef NS_ENABLE_TSF
+  ITfMessagePump* msgPump = nsTextStore::GetMessagePump();
+  if (msgPump) {
+    BOOL ret = FALSE;
+    HRESULT hr = msgPump->GetMessageW(aMsg, aWnd, aFirstMessage, aLastMessage,
+                                      &ret);
+    NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+    return ret;
+  }
+#endif // #ifdef NS_ENABLE_TSF
+  return ::GetMessageW(aMsg, aWnd, aFirstMessage, aLastMessage);
+}
+
 /* static */
 bool
 WinUtils::GetRegistryKey(HKEY aRoot,
diff --git a/widget/windows/WinUtils.h b/widget/windows/WinUtils.h
index b5e52d3bd315..27c9aec7dd5e 100644
--- a/widget/windows/WinUtils.h
+++ b/widget/windows/WinUtils.h
@@ -49,6 +49,16 @@ public:
   };
   static WinVersion GetWindowsVersion();
 
+  /**
+   * PeekMessage() and GetMessage() are wrapper methods for PeekMessageW(),
+   * GetMessageW(), ITfMessageMgr::PeekMessageW() and
+   * ITfMessageMgr::GetMessageW().
+   * Don't call the native APIs directly.  You MUST use these methods instead.
+   */
+  static bool PeekMessage(LPMSG aMsg, HWND aWnd, UINT aFirstMessage,
+                          UINT aLastMessage, UINT aOption);
+  static bool GetMessage(LPMSG aMsg, HWND aWnd, UINT aFirstMessage,
+                         UINT aLastMessage);
   /**
    * Gets the value of a string-typed registry value.
    *
diff --git a/widget/windows/nsAppShell.cpp b/widget/windows/nsAppShell.cpp
index 2e7240713e97..e9596eb7fb82 100644
--- a/widget/windows/nsAppShell.cpp
+++ b/widget/windows/nsAppShell.cpp
@@ -7,6 +7,7 @@
 #include "nsAppShell.h"
 #include "nsToolkit.h"
 #include "nsThreadUtils.h"
+#include "WinUtils.h"
 #include "WinTaskbar.h"
 #include "WinMouseScrollHandler.h"
 #include "nsWindowDefs.h"
@@ -15,6 +16,8 @@
 #include "mozilla/widget/AudioSession.h"
 #include "mozilla/HangMonitor.h"
 
+using namespace mozilla::widget;
+
 const PRUnichar* kAppShellEventId = L"nsAppShell:EventID";
 const PRUnichar* kTaskbarButtonEventId = L"TaskbarButtonCreated";
 
@@ -47,17 +50,20 @@ static bool PeekUIMessage(MSG* aMsg)
   // it may make different modifier key state or mouse cursor position between
   // them.
   if (mozilla::widget::MouseScrollHandler::IsWaitingInternalMessage() &&
-      ::PeekMessageW(aMsg, NULL, MOZ_WM_MOUSEWHEEL_FIRST,
-                     MOZ_WM_MOUSEWHEEL_LAST, PM_REMOVE)) {
+      WinUtils::PeekMessage(aMsg, NULL, MOZ_WM_MOUSEWHEEL_FIRST,
+                            MOZ_WM_MOUSEWHEEL_LAST, PM_REMOVE)) {
     return true;
   }
 
   MSG keyMsg, imeMsg, mouseMsg, *pMsg = 0;
   bool haveKeyMsg, haveIMEMsg, haveMouseMsg;
 
-  haveKeyMsg = ::PeekMessageW(&keyMsg, NULL, WM_KEYFIRST, WM_IME_KEYLAST, PM_NOREMOVE);
-  haveIMEMsg = ::PeekMessageW(&imeMsg, NULL, NS_WM_IMEFIRST, NS_WM_IMELAST, PM_NOREMOVE);
-  haveMouseMsg = ::PeekMessageW(&mouseMsg, NULL, WM_MOUSEFIRST, WM_MOUSELAST, PM_NOREMOVE);
+  haveKeyMsg = WinUtils::PeekMessage(&keyMsg, NULL, WM_KEYFIRST,
+                                     WM_IME_KEYLAST, PM_NOREMOVE);
+  haveIMEMsg = WinUtils::PeekMessage(&imeMsg, NULL, NS_WM_IMEFIRST,
+                                     NS_WM_IMELAST, PM_NOREMOVE);
+  haveMouseMsg = WinUtils::PeekMessage(&mouseMsg, NULL, WM_MOUSEFIRST,
+                                       WM_MOUSELAST, PM_NOREMOVE);
 
   if (haveKeyMsg) {
     pMsg = &keyMsg;
@@ -78,7 +84,8 @@ static bool PeekUIMessage(MSG* aMsg)
     return false;
   }
 
-  return ::PeekMessageW(aMsg, NULL, pMsg->message, pMsg->message, PM_REMOVE);
+  return WinUtils::PeekMessage(aMsg, NULL, pMsg->message,
+                               pMsg->message, PM_REMOVE);
 }
 
 /*static*/ LRESULT CALLBACK
@@ -223,7 +230,7 @@ nsAppShell::ProcessNextNativeEvent(bool mayWait)
 
     // Give priority to keyboard and mouse messages.
     if (uiMessage ||
-        PeekMessageW(&msg, NULL, 0, 0, PM_REMOVE)) {
+        WinUtils::PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
       gotMessage = true;
       if (msg.message == WM_QUIT) {
         ::PostQuitMessage(msg.wParam);
@@ -234,6 +241,12 @@ nsAppShell::ProcessNextNativeEvent(bool mayWait)
         mozilla::HangMonitor::NotifyActivity(
           uiMessage ? mozilla::HangMonitor::kUIActivity :
                       mozilla::HangMonitor::kActivityNoUIAVail);
+
+        if (msg.message >= WM_KEYFIRST && msg.message <= WM_KEYLAST &&
+            IMEHandler::ProcessRawKeyMessage(msg)) {
+          continue;  // the message is consumed.
+        }
+
         ::TranslateMessage(&msg);
         ::DispatchMessageW(&msg);
       }
diff --git a/widget/windows/nsIMM32Handler.cpp b/widget/windows/nsIMM32Handler.cpp
index 944a1dcbc5ab..54688765133c 100644
--- a/widget/windows/nsIMM32Handler.cpp
+++ b/widget/windows/nsIMM32Handler.cpp
@@ -526,9 +526,9 @@ nsIMM32Handler::OnIMEEndComposition(nsWindow* aWindow)
   // composition. Then, we should ignore the message and commit the composition
   // string at following WM_IME_COMPOSITION.
   MSG compositionMsg;
-  if (::PeekMessageW(&compositionMsg, aWindow->GetWindowHandle(),
-                     WM_IME_STARTCOMPOSITION, WM_IME_COMPOSITION,
-                     PM_NOREMOVE) &&
+  if (WinUtils::PeekMessage(&compositionMsg, aWindow->GetWindowHandle(),
+                            WM_IME_STARTCOMPOSITION, WM_IME_COMPOSITION,
+                            PM_NOREMOVE) &&
       compositionMsg.message == WM_IME_COMPOSITION &&
       IS_COMMITTING_LPARAM(compositionMsg.lParam)) {
     PR_LOG(gIMM32Log, PR_LOG_ALWAYS,
@@ -1012,11 +1012,11 @@ nsIMM32Handler::HandleComposition(nsWindow* aWindow,
   if (!mIsComposing) {
     MSG msg1, msg2;
     HWND wnd = aWindow->GetWindowHandle();
-    if (::PeekMessageW(&msg1, wnd, WM_IME_STARTCOMPOSITION, WM_IME_COMPOSITION,
-                       PM_NOREMOVE) &&
+    if (WinUtils::PeekMessage(&msg1, wnd, WM_IME_STARTCOMPOSITION,
+                              WM_IME_COMPOSITION, PM_NOREMOVE) &&
         msg1.message == WM_IME_STARTCOMPOSITION &&
-        ::PeekMessageW(&msg2, wnd, WM_IME_ENDCOMPOSITION, WM_IME_COMPOSITION,
-                       PM_NOREMOVE) &&
+        WinUtils::PeekMessage(&msg2, wnd, WM_IME_ENDCOMPOSITION,
+                              WM_IME_COMPOSITION, PM_NOREMOVE) &&
         msg2.message == WM_IME_COMPOSITION) {
       PR_LOG(gIMM32Log, PR_LOG_ALWAYS,
         ("IMM32: HandleComposition, Ignores due to find a WM_IME_STARTCOMPOSITION\n"));
diff --git a/widget/windows/nsTextStore.cpp b/widget/windows/nsTextStore.cpp
index a918d9da4245..4f632e64863e 100644
--- a/widget/windows/nsTextStore.cpp
+++ b/widget/windows/nsTextStore.cpp
@@ -132,6 +132,8 @@ private:
 /******************************************************************/
 
 ITfThreadMgr*           nsTextStore::sTsfThreadMgr   = NULL;
+ITfMessagePump*         nsTextStore::sMessagePump    = NULL;
+ITfKeystrokeMgr*        nsTextStore::sKeystrokeMgr   = NULL;
 ITfDisplayAttributeMgr* nsTextStore::sDisplayAttrMgr = NULL;
 ITfCategoryMgr*         nsTextStore::sCategoryMgr    = NULL;
 DWORD         nsTextStore::sTsfClientId  = 0;
@@ -579,9 +581,9 @@ nsTextStore::Destroy(void)
     // But by that time the text store is already destroyed,
     // so try to get the message early
     MSG msg;
-    if (::PeekMessageW(&msg, mWidget->GetWindowHandle(),
-                       sFlushTIPInputMessage, sFlushTIPInputMessage,
-                       PM_REMOVE)) {
+    if (WinUtils::PeekMessage(&msg, mWidget->GetWindowHandle(),
+                              sFlushTIPInputMessage, sFlushTIPInputMessage,
+                              PM_REMOVE)) {
       ::DispatchMessageW(&msg);
     }
   }
@@ -3156,6 +3158,16 @@ nsTextStore::Initialize(void)
     if (SUCCEEDED(CoCreateInstance(CLSID_TF_ThreadMgr, NULL,
           CLSCTX_INPROC_SERVER, IID_ITfThreadMgr,
           reinterpret_cast<void**>(&sTsfThreadMgr)))) {
+      DebugOnly<HRESULT> hr =
+        sTsfThreadMgr->QueryInterface(IID_ITfMessagePump,
+                                      reinterpret_cast<void**>(&sMessagePump));
+      MOZ_ASSERT(SUCCEEDED(hr));
+      MOZ_ASSERT(sMessagePump);
+      hr =
+        sTsfThreadMgr->QueryInterface(IID_ITfKeystrokeMgr,
+                                      reinterpret_cast<void**>(&sKeystrokeMgr));
+      MOZ_ASSERT(SUCCEEDED(hr));
+      MOZ_ASSERT(sKeystrokeMgr);
       PR_LOG(sTextStoreLog, PR_LOG_ALWAYS,
         ("TSF:   nsTextStore::Initialize() succeeded to "
          "create the thread manager, activating..."));
@@ -3216,6 +3228,11 @@ nsTextStore::Initialize(void)
         NS_LITERAL_STRING("Flush TIP Input Message").get());
   }
 
+  if (!sTsfThreadMgr) {
+    NS_IF_RELEASE(sMessagePump);
+    NS_IF_RELEASE(sKeystrokeMgr);
+  }
+
   PR_LOG(sTextStoreLog, PR_LOG_ALWAYS,
     ("TSF:   nsTextStore::Initialize(), sTsfThreadMgr=0x%p, "
      "sTsfClientId=0x%08X, sTsfTextStore=0x%p, sDisplayAttrMgr=0x%p, "
@@ -3237,9 +3254,40 @@ nsTextStore::Terminate(void)
   if (sTsfThreadMgr) {
     sTsfThreadMgr->Deactivate();
     NS_RELEASE(sTsfThreadMgr);
+    NS_RELEASE(sMessagePump);
+    NS_RELEASE(sKeystrokeMgr);
   }
 }
 
+// static
+bool
+nsTextStore::ProcessRawKeyMessage(const MSG& aMsg)
+{
+  if (!sKeystrokeMgr) {
+    return false; // not in TSF mode
+  }
+
+  if (aMsg.message == WM_KEYDOWN) {
+    BOOL eaten;
+    HRESULT hr = sKeystrokeMgr->TestKeyDown(aMsg.wParam, aMsg.lParam, &eaten);
+    if (FAILED(hr) || !eaten) {
+      return false;
+    }
+    hr = sKeystrokeMgr->KeyDown(aMsg.wParam, aMsg.lParam, &eaten);
+    return SUCCEEDED(hr) && eaten;
+  }
+  if (aMsg.message == WM_KEYUP) {
+    BOOL eaten;
+    HRESULT hr = sKeystrokeMgr->TestKeyUp(aMsg.wParam, aMsg.lParam, &eaten);
+    if (FAILED(hr) || !eaten) {
+      return false;
+    }
+    hr = sKeystrokeMgr->KeyUp(aMsg.wParam, aMsg.lParam, &eaten);
+    return SUCCEEDED(hr) && eaten;
+  }
+  return false;
+}
+
 /******************************************************************/
 /* nsTextStore::Composition                                       */
 /******************************************************************/
diff --git a/widget/windows/nsTextStore.h b/widget/windows/nsTextStore.h
index 5df666896c22..0262f49216a3 100644
--- a/widget/windows/nsTextStore.h
+++ b/widget/windows/nsTextStore.h
@@ -96,6 +96,9 @@ protected:
 public:
   static void     Initialize(void);
   static void     Terminate(void);
+
+  static bool     ProcessRawKeyMessage(const MSG& aMsg);
+
   static void     SetIMEOpenState(bool);
   static bool     GetIMEOpenState(void);
 
@@ -162,6 +165,11 @@ public:
     }
   }
 
+  static ITfMessagePump* GetMessagePump()
+  {
+    return sMessagePump;
+  }
+
   static void*    GetTextStore()
   {
     return static_cast<void*>(sTsfTextStore);
@@ -630,6 +638,10 @@ protected:
 
   // TSF thread manager object for the current application
   static ITfThreadMgr*  sTsfThreadMgr;
+  // sMessagePump is QI'ed from sTsfThreadMgr
+  static ITfMessagePump* sMessagePump;
+  // sKeystrokeMgr is QI'ed from sTsfThreadMgr
+  static ITfKeystrokeMgr* sKeystrokeMgr;
   // TSF display attribute manager
   static ITfDisplayAttributeMgr* sDisplayAttrMgr;
   // TSF category manager
diff --git a/widget/windows/nsWindow.cpp b/widget/windows/nsWindow.cpp
index 8ae839f8f854..e75a1bacc1f0 100644
--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -3806,7 +3806,7 @@ void nsWindow::RemoveMessageAndDispatchPluginEvent(UINT aFirstMsg,
     }
     msg = aFakeCharMessage->GetCharMessage(mWnd);
   } else {
-    ::GetMessageW(&msg, mWnd, aFirstMsg, aLastMsg);
+    WinUtils::GetMessage(&msg, mWnd, aFirstMsg, aLastMsg);
   }
   DispatchPluginEvent(msg);
 }
@@ -5639,10 +5639,10 @@ void nsWindow::PostSleepWakeNotification(const bool aIsSleepMode)
 void nsWindow::RemoveNextCharMessage(HWND aWnd)
 {
   MSG msg;
-  if (::PeekMessageW(&msg, aWnd,
-                     WM_KEYFIRST, WM_KEYLAST, PM_NOREMOVE | PM_NOYIELD) &&
+  if (WinUtils::PeekMessage(&msg, aWnd, WM_KEYFIRST, WM_KEYLAST,
+                            PM_NOREMOVE | PM_NOYIELD) &&
       (msg.message == WM_CHAR || msg.message == WM_SYSCHAR)) {
-    ::GetMessageW(&msg, aWnd, msg.message, msg.message);
+    WinUtils::GetMessage(&msg, aWnd, msg.message, msg.message);
   }
 }
 
@@ -6564,7 +6564,8 @@ LRESULT nsWindow::OnKeyDown(const MSG &aMsg,
   extraFlags.mDefaultPrevented = noDefault;
   MSG msg;
   BOOL gotMsg = aFakeCharMessage ||
-    ::PeekMessageW(&msg, mWnd, WM_KEYFIRST, WM_KEYLAST, PM_NOREMOVE | PM_NOYIELD);
+    WinUtils::PeekMessage(&msg, mWnd, WM_KEYFIRST, WM_KEYLAST,
+                          PM_NOREMOVE | PM_NOYIELD);
   // Enter and backspace are always handled here to avoid for example the
   // confusion between ctrl-enter and ctrl-J.
   if (DOMKeyCode == NS_VK_RETURN || DOMKeyCode == NS_VK_BACK ||
@@ -6591,7 +6592,8 @@ LRESULT nsWindow::OnKeyDown(const MSG &aMsg,
         RemoveMessageAndDispatchPluginEvent(WM_KEYFIRST, WM_KEYLAST);
         anyCharMessagesRemoved = true;
 
-        gotMsg = ::PeekMessageW (&msg, mWnd, WM_KEYFIRST, WM_KEYLAST, PM_NOREMOVE | PM_NOYIELD);
+        gotMsg = WinUtils::PeekMessage(&msg, mWnd, WM_KEYFIRST, WM_KEYLAST,
+                                       PM_NOREMOVE | PM_NOYIELD);
       }
     }
 
@@ -6633,7 +6635,7 @@ LRESULT nsWindow::OnKeyDown(const MSG &aMsg,
     }
 
     // If prevent default set for keydown, do same for keypress
-    ::GetMessageW(&msg, mWnd, msg.message, msg.message);
+    WinUtils::GetMessage(&msg, mWnd, msg.message, msg.message);
 
     if (msg.message == WM_DEADCHAR) {
       if (!PluginHasFocus())
diff --git a/widget/windows/winrt/MetroAppShell.cpp b/widget/windows/winrt/MetroAppShell.cpp
index c308f1088902..092e98d7946a 100644
--- a/widget/windows/winrt/MetroAppShell.cpp
+++ b/widget/windows/winrt/MetroAppShell.cpp
@@ -10,7 +10,9 @@
 #include "MetroApp.h"
 #include "nsIObserverService.h"
 #include "nsServiceManagerUtils.h"
+#include "WinUtils.h"
 
+using namespace mozilla::widget;
 using namespace mozilla::widget::winrt;
 using namespace Microsoft::WRL;
 using namespace Microsoft::WRL::Wrappers;
@@ -140,14 +142,14 @@ MetroAppShell::ProcessNextNativeEvent(bool mayWait)
   MSG msg;
 
   if (mayWait) {
-    if (!PeekMessageW(&msg, NULL, 0, 0, PM_NOREMOVE)) {
+    if (!WinUtils::PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE)) {
       WaitMessage();
     }
     ProcessOneNativeEventIfPresent();
     return true;
   }
 
-  if (PeekMessageW(&msg, NULL, 0, 0, PM_NOREMOVE)) {
+  if (WinUtils::PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE)) {
     ProcessOneNativeEventIfPresent();
     return true;
   }
diff --git a/widget/windows/winrt/MetroWidget.cpp b/widget/windows/winrt/MetroWidget.cpp
index 6d986aefc8d7..a8ded2a28b95 100644
--- a/widget/windows/winrt/MetroWidget.cpp
+++ b/widget/windows/winrt/MetroWidget.cpp
@@ -119,7 +119,10 @@ namespace {
     // processed.
     Log(L"  Inputs sent. Waiting for input messages to clear");
     MSG msg;
-    while (::PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
+    while (WinUtils::PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
+      if (nsTextStore::ProcessRawKeyMessage(msg)) {
+        continue;  // the message is consumed by TSF
+      }
       ::TranslateMessage(&msg);
       ::DispatchMessage(&msg);
       Log(L"    Dispatched 0x%x 0x%x 0x%x", msg.message, msg.wParam, msg.lParam);