diff --git a/README.md b/README.md
index ff7dd93e..1664120e 100644
--- a/README.md
+++ b/README.md
@@ -107,6 +107,7 @@ A compiler with C++14 support ([clang-3.4+](http://llvm.org/releases/download.ht
 - `xcb-util-xrm` *required for accessing X resources with `${xrdb:...}`*
 
 **Optional dependencies for extended module support:**
+- `xcb-xkb` *required by `internal/xkeyboard`*
 - `alsa-lib` *required by `internal/alsa`*
 - `libpulse` *required by `internal/pulseaudio`*
 - `i3-wm` *required by `internal/i3`*