1 files changed, 3 insertions, 1 deletions

diff --git a/src/buffer.c b/src/buffer.c
index fa5a9c85c2d..5ebcaa819d1 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -2081,7 +2081,9 @@ DEFUN ("set-buffer-multibyte", Fset_buffer_multibyte, Sset_buffer_multibyte,
 If FLAG is t, this makes the buffer a multibyte buffer.
 If FLAG is nil, this makes the buffer a single-byte buffer.
 The buffer contents remain unchanged as a sequence of bytes
-but the contents viewed as characters do change.  */)
+but the contents viewed as characters do change.
+If the multibyte flag was really changed, undo information of the
+current buffer is cleared.  */)
      (flag)
      Lisp_Object flag;
 {