diff --git a/src/ChangeLog b/src/ChangeLog
index 5dc29ff47ab..ab21a65a805 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,7 @@
 2013-08-16  Xue Fuqiao  <xfq.free@gmail.com>
 
+	* editfns.c (insert_before_markers): Mention overlay in the doc string.
+
 	* marker.c (set_marker): Remove documentation of undefined behavior.
 
 2013-08-15  Lars Magne Ingebrigtsen  <larsi@gnus.org>
diff --git a/src/editfns.c b/src/editfns.c
index 90346a88eb2..bbaeaea5240 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -2330,6 +2330,10 @@ to multibyte for insertion (see `unibyte-char-to-multibyte').
 If the current buffer is unibyte, multibyte strings are converted
 to unibyte for insertion.
 
+If an overlay begins at the insertion point, the inserted text falls
+outside the overlay; if a nonempty overlay ends at the insertion
+point, the inserted text falls inside that overlay.
+
 usage: (insert-before-markers &rest ARGS)  */)
   (ptrdiff_t nargs, Lisp_Object *args)
 {