1 files changed, 14 insertions, 7 deletions

diff --git a/lispref/text.texi b/lispref/text.texi
index 942fb2220a7..3d2fa870bac 100644
--- a/lispref/text.texi
+++ b/lispref/text.texi
@@ -1321,20 +1321,27 @@ preferred name is @code{buffer-disable-undo}.
 them from using up all available memory space, garbage collection trims
 them back to size limits you can set.  (For this purpose, the ``size''
 of an undo list measures the cons cells that make up the list, plus the
-strings of deleted text.)  Two variables control the range of acceptable
-sizes: @code{undo-limit} and @code{undo-strong-limit}.
+strings of deleted text.)  Three variables control the range of acceptable
+sizes: @code{undo-limit}, @code{undo-strong-limit} and
+@code{undo-outer-limit}.
 
-@defvar undo-limit
+@defopt undo-limit
 This is the soft limit for the acceptable size of an undo list.  The
 change group at which this size is exceeded is the last one kept.
-@end defvar
+@end defopt
 
-@defvar undo-strong-limit
+@defopt undo-strong-limit
 This is the upper limit for the acceptable size of an undo list.  The
 change group at which this size is exceeded is discarded itself (along
 with all older change groups).  There is one exception: the very latest
-change group is never discarded no matter how big it is.
-@end defvar
+change group is only discarded if it exceeds @code{undo-outer-limit}.
+@end defopt
+
+@defopt undo-outer-limit
+If at garbage collection time the undo info for the current command
+exceeds this limit, Emacs discards the info and prints a warning
+message.  This is a last ditch limit to prevent memory overflow.
+@end defopt
 
 @node Filling
 @comment  node-name,  next,  previous,  up