diff --git a/Doc/lib/libfuncs.tex b/Doc/lib/libfuncs.tex
index f276fb2..ed2427b 100644
--- a/Doc/lib/libfuncs.tex
+++ b/Doc/lib/libfuncs.tex
@@ -233,7 +233,7 @@
   expression.
 \end{funcdesc}
 
-\begin{funcdesc}{open}{filename\, \optional{mode\optional{\, bufsize}}}
+\begin{funcdesc}{open}{filename\optional{\, mode\optional{\, bufsize}}}
   Return a new file object (described earlier under Built-in Types).
   The first two arguments are the same as for \code{stdio}'s
   \code{fopen()}: \var{filename} is the file name to be opened,
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
diff --git a/Doc/libfuncs.tex b/Doc/libfuncs.tex
index f276fb2..ed2427b 100644
--- a/Doc/libfuncs.tex
+++ b/Doc/libfuncs.tex
@@ -233,7 +233,7 @@
   expression.
 \end{funcdesc}
 
-\begin{funcdesc}{open}{filename\, \optional{mode\optional{\, bufsize}}}
+\begin{funcdesc}{open}{filename\optional{\, mode\optional{\, bufsize}}}
   Return a new file object (described earlier under Built-in Types).
   The first two arguments are the same as for \code{stdio}'s
   \code{fopen()}: \var{filename} is the file name to be opened,
diff --git a/Doc/libsys.tex b/Doc/libsys.tex
index 9467415..fc71139 100644
--- a/Doc/libsys.tex
+++ b/Doc/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