1 files changed, 2 insertions, 1 deletions

diff --git a/src/buffer.h b/src/buffer.h
index 99f30d0315f..35a7d62685d 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -256,7 +256,8 @@ struct buffer
 #endif
     /* Alist of (FUNCTION . STRING) for each minor mode enabled in buffer. */
     Lisp_Object minor_modes;
-    /* t if "self-insertion" should overwrite */
+    /* t if "self-insertion" should overwrite; `binary' if it should also
+       overwrite newlines and tabs - for editing executables and the like.  */
     Lisp_Object overwrite_mode;
     /* non-nil means abbrev mode is on.  Expand abbrevs automatically. */
     Lisp_Object abbrev_mode;