9.15 Why doesn’t SPC complete file names anymore?

Starting with Emacs 22.1, SPC no longer completes file names in the minibuffer, so that file names with embedded spaces could be typed without the need to quote the spaces.

You can get the old behavior by binding SPC to minibuffer-complete-word in the minibuffer, as follows:

(define-key minibuffer-local-filename-completion-map (kbd "SPC")
  'minibuffer-complete-word)

(define-key minibuffer-local-must-match-filename-map (kbd "SPC")
  'minibuffer-complete-word)