diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,10 +1,17 @@
 # Revision history for wild-bind-indicator
 
+## 1.0.0.0  -- 2020-12-30
+
+* **MAJOR CHANGE**: Now it uses `gi-gtk` package, instead of `gtk` package.
+  Although this doesn't change the API of wild-bind-indicator, it changes the prerequisite packages/libraries significantly.
+  Thus we bumped the major version.
+* Now it uses `async` package to clean-up the WildBind action when the Gtk+ GUI finishes. Probably fixes #4 and #5a.
+* Confirm build with `containers-0.6.0.1`
+
 ## 0.2.0.0  -- 2018-01-01
 
 * Modify constraints of `withNumPadIndicator`, `wildBindWithIndicator`, `bindingHook` functions.
 * Add `adaptIndicator`, `toggleBinding` functions.
-
 
 ## 0.1.0.1  -- 2016-09-22
 
diff --git a/src/WildBind/Indicator.hs b/src/WildBind/Indicator.hs
--- a/src/WildBind/Indicator.hs
+++ b/src/WildBind/Indicator.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE OverloadedStrings, OverloadedLabels, PatternSynonyms #-}
 -- |
 -- Module: WildBind.Indicator
 -- Description: Graphical indicator for WildBind
@@ -31,34 +31,20 @@
        ) where
 
 import Control.Applicative ((<$>))
-import Control.Concurrent (forkFinally, rtsSupportsBoundThreads)
-import Control.Exception (throwIO)
+import Control.Concurrent
+  (rtsSupportsBoundThreads, newEmptyMVar, putMVar, takeMVar)
+import Control.Concurrent.Async (withAsync)
+import Control.Exception (throwIO, finally)
 import Control.Monad (void, forM_)
 import Control.Monad.IO.Class (liftIO)
 import Control.Monad.Trans.Reader (ReaderT, runReaderT, ask)
 import Data.IORef (newIORef, readIORef)
 import qualified Data.Map as M
 import Data.Monoid (mconcat, First(First))
-import Data.Text (Text)
-import Graphics.UI.Gtk
-  ( initGUI, mainGUI, postGUIAsync, postGUISync, mainQuit,
-    Window, windowNew, windowSetKeepAbove, windowSkipPagerHint,
-    windowSkipTaskbarHint, windowAcceptFocus, windowFocusOnMap,
-    windowSetTitle, windowMove,
-    AttrOp((:=)),
-    widgetShowAll, widgetSetSizeRequest, widgetVisible, widgetHide,
-    Table, tableNew, tableAttachDefaults,
-    buttonNew, buttonSetAlignment,
-    Label, labelNew, labelSetLineWrap, labelSetJustify, Justification(JustifyLeft), labelSetText,
-    miscSetAlignment,
-    containerAdd,
-    deleteEvent,
-    statusIconNewFromFile, statusIconPopupMenu,
-    Menu, menuNew, menuItemNewWithMnemonic, menuItemActivated, menuPopup,
-    checkMenuItemNewWithMnemonic, checkMenuItemSetActive, checkMenuItemToggled
-  )
-import qualified Graphics.UI.Gtk as G (get, set, on)
+import Data.Text (Text, pack)
+import Data.Word (Word32)
 import System.IO (stderr, hPutStrLn)
+import System.Environment (getArgs)
 
 import WildBind ( ActionDescription, Option(optBindingHook),
                   FrontEnd(frontDefaultDescription), Binding, Binding',
@@ -70,6 +56,31 @@
 import Paths_wild_bind_indicator (getDataFileName)
 
 
+---- Imports about Gtk
+import GI.Gdk.Functions (threadsAddIdle)
+import GI.GLib.Constants (pattern PRIORITY_DEFAULT)
+import GI.Gtk 
+  ( -- Data.GI.Base.Attributes
+    AttrOp((:=))
+  )
+import qualified GI.Gtk as GIAttr (set, get, on)
+import GI.Gtk.Enums (WindowType(..), Justification(..))
+import qualified GI.Gtk.Functions as GIFunc
+import GI.Gtk.Objects.Button (buttonNew, buttonSetAlignment)
+import GI.Gtk.Objects.CheckMenuItem (checkMenuItemNewWithMnemonic, checkMenuItemSetActive)
+import GI.Gtk.Objects.Container (containerAdd)
+import GI.Gtk.Objects.Label (Label, labelNew, labelSetLineWrap, labelSetJustify, labelSetText)
+import GI.Gtk.Objects.Menu (Menu, menuNew, menuPopup)
+import GI.Gtk.Objects.MenuItem (menuItemNewWithMnemonic)
+import GI.Gtk.Objects.Misc (miscSetAlignment)
+import GI.Gtk.Objects.StatusIcon (statusIconNewFromFile)
+import GI.Gtk.Objects.Table (Table, tableNew, tableAttachDefaults)
+import GI.Gtk.Objects.Widget (Widget, widgetSetSizeRequest, widgetShowAll, widgetHide)
+import GI.Gtk.Objects.Window
+  ( Window, windowNew, windowSetKeepAbove, windowSetTitle, windowMove
+  )
+
+
 -- | Indicator interface. @s@ is the front-end state, @i@ is the input
 -- type.
 data Indicator s i =
@@ -166,40 +177,38 @@
 withNumPadIndicator :: (NumPadPosition i, Enum i, Bounded i) => (Indicator s i -> IO ()) -> IO ()
 withNumPadIndicator action = if rtsSupportsBoundThreads then impl else error_impl where
   error_impl = throwIO $ userError "You need to build with -threaded option when you use WildBind.Indicator.withNumPadIndicator function."
+  textArgs = fmap (map pack) $ getArgs
   impl = do
-    void $ initGUI
+    void $ (GIFunc.init . Just) =<< textArgs
     conf <- numPadConfig
     indicator <- createMainWinAndIndicator conf
     status_icon <- createStatusIcon conf indicator
     status_icon_ref <- newIORef status_icon
-    mainGUI
-    void $ readIORef status_icon_ref -- to prevent status_icon from being garbage-collected. See https://github.com/gtk2hs/gtk2hs/issues/60
+    withAsync (asyncAction indicator) $ \_ -> do
+      GIFunc.main
+      void $ readIORef status_icon_ref -- to prevent status_icon from being garbage-collected. See https://github.com/gtk2hs/gtk2hs/issues/60
   createMainWinAndIndicator conf = flip runReaderT conf $ do
     win <- newNumPadWindow
     (tab, updater) <- newNumPadTable
-    liftIO $ containerAdd win tab
+    containerAdd win tab
     let indicator = Indicator
           { updateDescription = \i d -> updater i d,
-            getPresence = G.get win widgetVisible,
+            getPresence = GIAttr.get win #visible,
             setPresence = \visible -> if visible then widgetShowAll win else widgetHide win,
-            quit = mainQuit,
+            quit = GIFunc.mainQuit,
             allButtons = enumFromTo minBound maxBound
           }
-    liftIO $ void $ G.on win deleteEvent $ do
-      liftIO $ widgetHide win
+    void $ GIAttr.on win #deleteEvent $ \_ -> do
+      widgetHide win
       return True -- Do not emit 'destroy' signal
-    liftIO $ void $ forkFinally (action $ transportIndicator indicator) finalAction
     return indicator
-  finalAction ret = do
-    case ret of
-      Right _ -> return ()
-      Left exception -> hPutStrLn stderr ("Fatal Error from WildBind: " ++ show exception)
-    postGUIAsync mainQuit
+  asyncAction indicator =
+    (action $ transportIndicator indicator) `finally` (postGUIAsync GIFunc.mainQuit) 
   createStatusIcon conf indicator = do
     status_icon <- statusIconNewFromFile $ confIconPath conf
-    void $ G.on status_icon statusIconPopupMenu $ \mbutton time -> do
+    void $ GIAttr.on status_icon #popupMenu $ \button time -> do
       menu <- makeStatusMenu indicator
-      menuPopup menu $ (\button -> return (button, time)) =<< mbutton
+      menuPopup menu (Nothing :: Maybe Widget) (Nothing :: Maybe Widget) Nothing button time
     return status_icon
 
 
@@ -218,17 +227,17 @@
   
 newNumPadWindow :: NumPadContext Window
 newNumPadWindow = do
-  win <- liftIO $ windowNew
-  liftIO $ windowSetKeepAbove win True
-  liftIO $ G.set win [ windowSkipPagerHint := True,
-                       windowSkipTaskbarHint := True,
-                       windowAcceptFocus := False,
-                       windowFocusOnMap := False
-                     ]
-  liftIO $ windowSetTitle win ("WildBind Description" :: Text)
-  win_x <- confWindowX <$> ask
-  win_y <- confWindowY <$> ask
-  liftIO $ windowMove win win_x win_y
+  win <- windowNew WindowTypeToplevel
+  windowSetKeepAbove win True
+  GIAttr.set win [ #skipPagerHint := True,
+                   #skipTaskbarHint := True,
+                   #acceptFocus := False,
+                   #focusOnMap := False
+                 ]
+  windowSetTitle win "WildBind Description"
+  win_x <- (fromIntegral . confWindowX) <$> ask
+  win_y <- (fromIntegral . confWindowY) <$> ask
+  windowMove win win_x win_y
   return win
 
 -- | Get the action to describe @i@, if that @i@ is supported. This is
@@ -237,9 +246,9 @@
 
 newNumPadTable :: NumPadPosition i => NumPadContext (Table, (i -> ActionDescription -> IO ()))
 newNumPadTable = do
-  tab <- liftIO $ tableNew 5 4 False
+  tab <- tableNew 5 4 False
   -- NumLock is unboundable, so it's treatd in a different way from others.
-  (\label -> liftIO $ labelSetText label ("NumLock" :: Text)) =<< addButton tab 0 1 0 1
+  (\label -> labelSetText label "NumLock") =<< addButton tab 0 1 0 1
   descript_action_getter <-
     fmap mconcat $ sequence $
       [ getter NumLDivide $ addButton tab 1 2 0 1,
@@ -269,19 +278,19 @@
       label <- get_label
       return $ \in_key -> First (if in_key == bound_key then Just $ labelSetText label else Nothing)
 
-addButton :: Table -> Int -> Int -> Int -> Int -> NumPadContext Label
+addButton :: Table -> Word32 -> Word32 -> Word32 -> Word32 -> NumPadContext Label
 addButton tab left right top bottom = do
-  lab <- liftIO $ labelNew (Nothing :: Maybe Text)
-  liftIO $ labelSetLineWrap lab True
-  liftIO $ miscSetAlignment lab 0 0.5
-  liftIO $ labelSetJustify lab JustifyLeft
-  button <- liftIO $ buttonNew
-  liftIO $ buttonSetAlignment button (0, 0.5)
-  liftIO $ containerAdd button lab
-  liftIO $ tableAttachDefaults tab button left right top bottom
-  bw <- confButtonWidth <$> ask
-  bh <- confButtonHeight <$> ask
-  liftIO $ widgetSetSizeRequest lab (bw * (right - left)) (bh * (bottom - top))
+  lab <- labelNew Nothing
+  labelSetLineWrap lab True
+  miscSetAlignment lab 0 0.5
+  labelSetJustify lab JustificationLeft
+  button <- buttonNew
+  buttonSetAlignment button 0 0.5
+  containerAdd button lab
+  tableAttachDefaults tab button left right top bottom
+  bw <- (fromIntegral . confButtonWidth) <$> ask
+  bh <- (fromIntegral . confButtonHeight) <$> ask
+  widgetSetSizeRequest lab (bw * fromIntegral (right - left)) (bh * fromIntegral (bottom - top))
   return lab
 
 makeStatusMenu :: Indicator s i -> IO Menu
@@ -292,15 +301,15 @@
     containerAdd menu =<< makeToggler
     return menu
   makeQuitItem = do
-    quit_item <- menuItemNewWithMnemonic ("_Quit" :: Text)
+    quit_item <- menuItemNewWithMnemonic "_Quit"
     widgetShowAll quit_item
-    void $ G.on quit_item menuItemActivated (quit ind)
+    void $ GIAttr.on quit_item #activate (quit ind)
     return quit_item
   makeToggler = do
-    toggler <- checkMenuItemNewWithMnemonic ("_Toggle description" :: Text)
+    toggler <- checkMenuItemNewWithMnemonic "_Toggle description"
     widgetShowAll toggler
     checkMenuItemSetActive toggler =<< getPresence ind
-    void $ G.on toggler checkMenuItemToggled (togglePresence ind)
+    void $ GIAttr.on toggler #toggled (togglePresence ind)
     return toggler
 
 -- | Map input type of 'Indicator', so that it can adapt to the new
@@ -333,3 +342,23 @@
 toggleBinding ind button = binding $ map (\input -> (input, Action "Toggle description" $ togglePresence ind)) help_likes
   where
     help_likes = filter ((== button) . toNumPad) $ enumFromTo minBound maxBound
+
+
+-- | Schedule the given action to be executed by Gdk. The given action
+-- can include manipulation of Gtk+ objects. This function can be
+-- called by a thread that is different from the Gtk+ main loop
+-- thread. This function doesn't wait for the given action to finish.
+--
+-- See https://github.com/haskell-gi/haskell-gi/wiki/Using-threads-in-Gdk-and-Gtk--programs
+postGUIAsync :: IO () -> IO ()
+postGUIAsync action = void $ threadsAddIdle PRIORITY_DEFAULT (action >> return False)
+
+-- | Similar to 'postGUIAsync', but this function waits for the action
+-- to finish.
+postGUISync :: IO a -> IO a
+postGUISync action = do
+  mret <- newEmptyMVar
+  postGUIAsync $ do
+    ret <- action
+    putMVar mret ret
+  takeMVar mret
diff --git a/wild-bind-indicator.cabal b/wild-bind-indicator.cabal
--- a/wild-bind-indicator.cabal
+++ b/wild-bind-indicator.cabal
@@ -1,5 +1,5 @@
 name:                   wild-bind-indicator
-version:                0.2.0.0
+version:                1.0.0.0
 author:                 Toshio Ito <debug.ito@gmail.com>
 maintainer:             Toshio Ito <debug.ito@gmail.com>
 license:                BSD3
@@ -19,15 +19,18 @@
   default-language:     Haskell2010
   hs-source-dirs:       src
   ghc-options:          -Wall -fno-warn-unused-imports
-  other-extensions:     OverloadedStrings
+  other-extensions:     OverloadedStrings, OverloadedLabels
   exposed-modules:      WildBind.Indicator
   other-modules:        Paths_wild_bind_indicator
-  build-depends:        base >=4.6 && <5.0,
+  build-depends:        base >=4.9 && <5.0,
                         wild-bind >=0.1.0 && <0.2,
                         transformers >=0.3.0 && <0.6,
-                        gtk >=0.14.2 && <0.15,
+                        gi-gtk >=3.0.3 && <3.1,
+                        gi-gdk >=3.0.3 && <3.1,
+                        gi-glib >=2.0.3 && <2.1,
+                        async >=2.1.1.1 && <2.3,
                         text >=1.2.0 && <1.3,
-                        containers >=0.5.0 && <0.6
+                        containers >=0.5.0 && <0.7
 
 -- executable wild-bind-indicator
 --   default-language:     Haskell2010