diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,10 @@
 # Revision history for wild-bind-x11
 
+## 0.2.0.11  -- 2020-12-30
+
+* Call [XInitThreads](https://linux.die.net/man/3/xinitthreads) at the start of `withX11Front'`.
+  It seemd no problem without this function, but the manual says you need it...
+
 ## 0.2.0.10  -- 2020-06-21
 
 * Confirm test with `base-4.14.0.0`
diff --git a/src/WildBind/X11/Internal/FrontEnd.hs b/src/WildBind/X11/Internal/FrontEnd.hs
--- a/src/WildBind/X11/Internal/FrontEnd.hs
+++ b/src/WildBind/X11/Internal/FrontEnd.hs
@@ -115,6 +115,7 @@
               -> IO a
 withX11Front' func_name = if rtsSupportsBoundThreads then impl else error_impl where
   impl = runContT $ do
+    liftIO $ doInitThreads
     disp <- ContT $ bracket openMyDisplay Xlib.closeDisplay
     keymask_map <- liftIO $ getKeyMaskMap disp
     notif_disp <- ContT $ bracket openMyDisplay Xlib.closeDisplay
@@ -127,6 +128,10 @@
     liftIO $ Ndeb.notify debouncer
     return $ X11Front disp debouncer awin_ref pending_events keymask_map grab_man
   error_impl _ = throwIO $ userError ("You need to build with -threaded option when you use " ++ func_name ++ " function.")
+  doInitThreads = do
+    ret <- Xlib.initThreads
+    when (ret == 0) $ do
+      throwIO $ userError ("Failure in XInitThreads.")
 
 
 tellElem :: Monad m => a -> WriterT [a] m ()
diff --git a/wild-bind-x11.cabal b/wild-bind-x11.cabal
--- a/wild-bind-x11.cabal
+++ b/wild-bind-x11.cabal
@@ -1,5 +1,5 @@
 name:                   wild-bind-x11
-version:                0.2.0.10
+version:                0.2.0.11
 author:                 Toshio Ito <debug.ito@gmail.com>
 maintainer:             Toshio Ito <debug.ito@gmail.com>
 license:                BSD3