diff --git a/ses.el b/ses.el
index a2e6033..06a3d51 100644
--- a/ses.el
+++ b/ses.el
@@ -3457,7 +3457,9 @@ With a \\[universal-argument] prefix arg, prompt the user.
 The top row is row 1.  Selecting row 0 displays the default header row."
   (interactive
    (list (if (numberp current-prefix-arg) current-prefix-arg
-	   (let ((currow (1+ (car (ses-sym-rowcol ses--curcell)))))
+	   (let* ((curcell (or (ses--cell-at-pos (point))
+                               (user-error "Invalid header-row")))
+         	  (currow (1+ (car (ses-sym-rowcol curcell)))))
 	     (if current-prefix-arg
 		 (read-number "Header row: " currow)
 	       currow)))))