diff --git a/Doc/lib/libos.tex b/Doc/lib/libos.tex
index c956ab1b22f..aafe7b19775 100644
--- a/Doc/lib/libos.tex
+++ b/Doc/lib/libos.tex
@@ -1193,7 +1193,7 @@ Availability: \UNIX.
 \end{funcdesc}
 
 \begin{funcdesc}{waitpid}{pid, options}
-The details of this function differ on \UNIX and Windows.
+The details of this function differ on \UNIX{} and Windows.
 
 On \UNIX:
 Wait for completion of a child process given by process id \var{pid},