1 files changed, 3 insertions, 1 deletions

diff --git a/src/termhooks.h b/src/termhooks.h
index 97c128ba4e2..b5171bf1229 100644
--- a/src/termhooks.h
+++ b/src/termhooks.h
@@ -116,7 +116,9 @@ enum event_kind
                                    .frame_or_window gives the frame
                                    the wheel event occurred in.
                                    .timestamp gives a timestamp (in
-                                   milliseconds) for the event.  */
+                                   milliseconds) for the event.
+                                   .arg may contain the number of
+                                   lines to scroll.  */
   HORIZ_WHEEL_EVENT,            /* A wheel event generated by a second
                                    horizontal wheel that is present on some
                                    mice. See WHEEL_EVENT.  */