Fix warning that texcheck complained about.
diff --git a/Doc/api/init.tex b/Doc/api/init.tex
index 73d7bbe..9225f69 100644
--- a/Doc/api/init.tex
+++ b/Doc/api/init.tex
@@ -184,7 +184,7 @@
variable in the top-level \file{Makefile} and the
\longprogramopt{prefix} argument to the \program{configure} script
at build time. The value is available to Python code as
- \code{sys.prefix}. It is only useful on \UNIX. See also the next
+ \code{sys.prefix}. It is only useful on \UNIX{}. See also the next
function.
\end{cfuncdesc}