diff --git a/Doc/libstdwin.tex b/Doc/libstdwin.tex
index 514252f..91dc1af 100644
--- a/Doc/libstdwin.tex
+++ b/Doc/libstdwin.tex
@@ -20,7 +20,7 @@
 This module defines several new object types and functions that
 provide access to the functionality of STDWIN.
 
-On Unix running X11, it can only be used if the \code{DISPLAY}
+On \UNIX{} running X11, it can only be used if the \code{DISPLAY}
 environment variable is set or an explicit \samp{-display
 \var{displayname}} argument is passed to the Python interpreter.