cosmetics/typos
diff --git a/Doc/lib/libsys.tex b/Doc/lib/libsys.tex
index 9467415..fc71139 100644
--- a/Doc/lib/libsys.tex
+++ b/Doc/lib/libsys.tex
@@ -90,7 +90,7 @@
 it to a larger value may increase performance for programs using
 threads.  Setting it to a value <= 0 checks every virtual instruction,
 maximizing responsiveness as well as overhead.
-\end{datadesc}
+\end{funcdesc}
 
 \begin{funcdesc}{settrace}{tracefunc}
   Set the system's trace function, which allows you to implement a