diff --git a/src/buffer.c b/src/buffer.c
index 57d88b0f791..6cbaabf85ec 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -5559,7 +5559,8 @@ its hooks should not expect certain variables such as
 
   DEFVAR_PER_BUFFER ("mode-name", &current_buffer->mode_name,
                      Qnil,
-		     doc: /* Pretty name of current buffer's major mode (a string).  */);
+		     doc: /* Pretty name of current buffer's major mode.
+Usually a string.  See `mode-line-format' for other possible forms.  */);
 
   DEFVAR_PER_BUFFER ("local-abbrev-table", &current_buffer->abbrev_table, Qnil,
 		     doc: /* Local (mode-specific) abbrev table of current buffer.  */);