diff --git a/widget/gtk2/nsGtkKeyUtils.cpp b/widget/gtk2/nsGtkKeyUtils.cpp
index 2969c3255980..38a8df853a84 100644
--- a/widget/gtk2/nsGtkKeyUtils.cpp
+++ b/widget/gtk2/nsGtkKeyUtils.cpp
@@ -518,22 +518,23 @@ KeymapWrapper::GetCurrentModifierState()
 /* static */ bool
 KeymapWrapper::AreModifiersCurrentlyActive(Modifiers aModifiers)
 {
-    KeymapWrapper* keymapWrapper = GetInstance();
     guint modifierState = GetCurrentModifierState();
-    return keymapWrapper->AreModifiersActive(aModifiers, modifierState);
+    return AreModifiersActive(aModifiers, modifierState);
 }
 
-bool
+/* static */ bool
 KeymapWrapper::AreModifiersActive(Modifiers aModifiers,
-                                  guint aModifierState) const
+                                  guint aModifierState)
 {
     NS_ENSURE_TRUE(aModifiers, false);
+
+    KeymapWrapper* keymapWrapper = GetInstance();
     for (PRUint32 i = 0; i < sizeof(Modifier) * 8 && aModifiers; i++) {
         Modifier modifier = static_cast<Modifier>(1 << i);
         if (!(aModifiers & modifier)) {
             continue;
         }
-        if (!(aModifierState & GetModifierMask(modifier))) {
+        if (!(aModifierState & keymapWrapper->GetModifierMask(modifier))) {
             return false;
         }
         aModifiers &= ~modifier;
diff --git a/widget/gtk2/nsGtkKeyUtils.h b/widget/gtk2/nsGtkKeyUtils.h
index 1c75b85b1aa2..8d1ffcc7924c 100644
--- a/widget/gtk2/nsGtkKeyUtils.h
+++ b/widget/gtk2/nsGtkKeyUtils.h
@@ -117,6 +117,20 @@ public:
      */
     static bool AreModifiersCurrentlyActive(Modifiers aModifiers);
 
+    /**
+     * AreModifiersActive() just checks whether aModifierState indicates
+     * all modifiers in aModifiers are active or not.
+     *
+     * @param aModifiers        One or more of Modifier values except
+     *                          NOT_MODIFIER.
+     * @param aModifierState    GDK's modifier states.
+     * @return                  TRUE if aGdkModifierType indecates all of
+     *                          modifiers in aModifier are active.
+     *                          Otherwise, FALSE.
+     */
+    static bool AreModifiersActive(Modifiers aModifiers,
+                                   guint aModifierState);
+
     /**
      * InitInputEvent() initializes the aInputEvent with aModifierState.
      */
@@ -210,20 +224,6 @@ protected:
     static const char* GetModifierName(Modifier aModifier);
 #endif // PR_LOGGING
 
-    /**
-     * AreModifiersActive() just checks whether aModifierState indicates
-     * all modifiers in aModifiers are active or not.
-     *
-     * @param aModifiers        One or more of Modifier values except
-     *                          NOT_MODIFIER.
-     * @param aModifierState    GDK's modifier states.
-     * @return                  TRUE if aGdkModifierType indecates all of
-     *                          modifieres in aModifier are active.
-     *                          Otherwise, FALSE.
-     */
-    bool AreModifiersActive(Modifiers aModifiers,
-                            guint aModifierState) const;
-
     /**
      * mGdkKeymap is a wrapped instance by this class.
      */
diff --git a/widget/gtk2/nsWindow.cpp b/widget/gtk2/nsWindow.cpp
index e2c2155fbcc4..9de734e8b125 100644
--- a/widget/gtk2/nsWindow.cpp
+++ b/widget/gtk2/nsWindow.cpp
@@ -2922,7 +2922,8 @@ static bool
 IsCtrlAltTab(GdkEventKey *aEvent)
 {
     return aEvent->keyval == GDK_Tab &&
-        aEvent->state & GDK_CONTROL_MASK && aEvent->state & GDK_MOD1_MASK;
+        KeymapWrapper::AreModifiersActive(
+            KeymapWrapper::CTRL | KeymapWrapper::ALT, aEvent->state);
 }
 
 bool