Oops, missed a \POSIX{} in an index entry.
diff --git a/Doc/lib/libthread.tex b/Doc/lib/libthread.tex
index 911c145..ae11823 100644
--- a/Doc/lib/libthread.tex
+++ b/Doc/lib/libthread.tex
@@ -16,7 +16,7 @@
 IRIX, Solaris 2.x, as well as on systems that have a \POSIX{} thread
 (a.k.a. ``pthread'') implementation.
 \index{pthreads}
-\indexii{threads}{posix}
+\indexii{threads}{\POSIX{}}
 
 It defines the following constant and functions:
 
diff --git a/Doc/libthread.tex b/Doc/libthread.tex
index 911c145..ae11823 100644
--- a/Doc/libthread.tex
+++ b/Doc/libthread.tex
@@ -16,7 +16,7 @@
 IRIX, Solaris 2.x, as well as on systems that have a \POSIX{} thread
 (a.k.a. ``pthread'') implementation.
 \index{pthreads}
-\indexii{threads}{posix}
+\indexii{threads}{\POSIX{}}
 
 It defines the following constant and functions: