diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,11 @@
 # Revision history for wild-bind-x11
 
+## 0.2.0.12  -- 2021-03-25
+
+* Confirm test with `base-4.15.0.0`
+* Documentation update: Now `withFrontEnd` should be called as early as possible in `main`.
+  See https://github.com/debug-ito/wild-bind/issues/6
+
 ## 0.2.0.11  -- 2020-12-30
 
 * Call [XInitThreads](https://linux.die.net/man/3/xinitthreads) at the start of `withX11Front'`.
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
@@ -88,6 +88,10 @@
 -- Code using this function must be compiled
 -- __with @-threaded@ option enabled__ in @ghc@. Otherwise, it aborts.
 --
+-- Basically you should call this function directly under @main@. This
+-- is because this function calls some low-level X11 functions to
+-- initialize the X11 client, which should be done first.
+--
 -- Because this 'FrontEnd' currently uses @XGrabKey(3)@ to get the
 -- input, it may cause some weird behavior such as:
 --
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:                0.2.0.11
+version:                0.2.0.12
 author:                 Toshio Ito <debug.ito@gmail.com>
 maintainer:             Toshio Ito <debug.ito@gmail.com>
 license:                BSD3
@@ -28,7 +28,7 @@
                         WildBind.X11.Internal.NotificationDebouncer
   other-modules:        WildBind.X11.Internal.FrontEnd,
                         WildBind.X11.Internal.GrabMan
-  build-depends:        base >=4.6 && <4.15,
+  build-depends:        base >=4.6 && <4.16,
                         wild-bind >=0.1.0 && <0.2,
                         text >=1.2.0 && <1.3,
                         X11 >=1.6.1 && <1.10,
@@ -65,6 +65,7 @@
                         WildBind.X11.EmulateSpec,
                         WildBind.X11.Internal.NotificationDebouncerSpec,
                         WildBind.X11.TestUtil
+  build-tool-depends:   hspec-discover:hspec-discover
   build-depends:        base, wild-bind-x11,
                         wild-bind, X11, text, transformers,
                         hspec >=2.1.7,
