--- mm-encode.el~	2009-01-22 08:09:02 +0000
+++ mm-encode.el	2009-09-03 11:24:11 +0000
@@ -148,9 +148,11 @@
 	      (mm-content-transfer-encoding mime-type)))
 	 (bits (mm-body-7-or-8)))
     ;; We force buffers that are 7bit to be unencoded, no matter
-    ;; what the preferred encoding is.
-    ;; Only if the buffers don't contain lone lines.
-    (when (and (eq bits '7bit) (not (mm-long-lines-p 76)))
+    ;; what the preferred encoding is, except that the MIME-type is
+    ;; application/octet-stream or the buffers contain long lines.
+    (when (and (eq bits '7bit)
+	       (not (string-equal mime-type "application/octet-stream"))
+	       (not (mm-long-lines-p 76)))
       (setq encoding bits))
     (mm-encode-content-transfer-encoding encoding mime-type)
     encoding))