1 files changed, 7 insertions, 1 deletions

diff --git a/src/buffer.c b/src/buffer.c
index 2ca4332bca2..a5099fc2487 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -5782,7 +5782,13 @@ An entry (nil PROPERTY VALUE BEG . END) indicates that a text property
 was modified between BEG and END.  PROPERTY is the property name,
 and VALUE is the old value.
 
-An entry (FUN-NAME . ARGS) means undo the change with (apply FUN-NAME ARGS).
+An entry (apply FUN-NAME . ARGS) means undo the change with
+\(apply FUN-NAME ARGS).
+
+An entry (apply DELTA BEG END FUN-NAME . ARGS) supports selective undo
+in the active region.  BEG and END is the range affected by this entry
+and DELTA is the number of bytes added or deleted in that range by
+this change.
 
 An entry (MARKER . DISTANCE) indicates that the marker MARKER
 was adjusted in position by the offset DISTANCE (an integer).