diff --git a/mu4e/mu4e-draft.el b/mu4e/mu4e-draft.el
index dca747f5..8a06e048 100644
--- a/mu4e/mu4e-draft.el
+++ b/mu4e/mu4e-draft.el
@@ -302,10 +302,15 @@ separator is never written to the message file. Also see
       ;; search for the first empty line
       (goto-char (point-min))
       (if (search-forward-regexp "^$" nil t)
-	  (replace-match sepa)
-	  (progn ;; no empty line? then prepend one
-	    (goto-char (point-max))
-	    (insert "\n" sepa))))))
+          (progn
+            (replace-match sepa)
+            ;; `message-narrow-to-headers` searches for a `mail-header-separator` followed by a new
+            ;; line. Therefore, we must insert a newline if on the last line of the buffer.
+            (when (= (point) (point-max))
+              (insert "\n")))
+          (progn ;; no empty line? then prepend one
+            (goto-char (point-max))
+            (insert "\n" sepa))))))
 
 (defun mu4e~draft-remove-mail-header-separator ()
   "Remove `mail-header-separator; we do this before saving a