--- a/man/lispref/errors.texi	Mon Aug 13 11:01:58 2007 +0200
+++ b/man/lispref/errors.texi	Mon Aug 13 11:03:08 2007 +0200
@@ -125,6 +125,8 @@
 
 @item setting-constant
 @code{"Attempt to set a constant symbol"}@* 
+The values of the symbols @code{nil} and @code{t}
+may not be changed.@*
 @xref{Constant Variables, , Variables that Never Change}.
 
 @c XEmacs feature
@@ -140,6 +142,10 @@
 @item undefined-keystroke-sequence
 @code{"Undefined keystroke sequence"}@*
 
+@c XEmacs feature
+@item underflow-error
+@code{"Arithmetic underflow error"}@*
+
 @ignore FSF Emacs only
 @item undefined-color
 @code{"Undefined color"}@*