Here's an easier way to exhibit the bug. The only difference is whether gutters are visible: $ xemacs -vanilla -batch -eval ' (let (x y) (setq gutter-visible-p (set-specifier default-gutter-visible-p nil)) (insert "foo") (beginning-of-line) (re-search-forward "foo") (setq x (match-data t)) (split-window-vertically) (other-window 1) (setq y (match-data t)) (message "%s %s" x y))' (1 4) (1 4) $ xemacs -vanilla -batch -eval ' (let (x y) (insert "foo") (beginning-of-line) (re-search-forward "foo") (setq x (match-data t)) (split-window-vertically) (other-window 1) (setq y (match-data t)) (message "%s %s" x y))' (1 4) (0 1)