* lisp/help-fns.el (describe-variable):

Check {file,dir}-local-variables-alist, and buffer-file-name,
in the correct buffer.

This seems to have Just Worked in 24.3 - when and why did it change?

lisp/ChangeLog

+2014-02-08  Glenn Morris  <rgm@gnu.org>
+
+	* help-fns.el (describe-variable):
+	Check {file,dir}-local-variables-alist, and buffer-file-name,
+	in the correct buffer.
+
 2014-02-08  Ingo Lohmar  <i.lohmar@gmail.com>
 
 	* help-fns.el (describe-variable): Fix the case where

lisp/help-fns.el

@@ -911,13 +911,18 @@ if it is given a local binding.\n")))
 			     (t ".")))
                 (terpri))
 
-	      (when (member (cons variable val) file-local-variables-alist)
+	      (when (member (cons variable val)
+                            (with-current-buffer buffer
+                              file-local-variables-alist))
 		(setq extra-line t)
-		(if (member (cons variable val) dir-local-variables-alist)
-		    (let ((file (and (buffer-file-name)
-                                      (not (file-remote-p (buffer-file-name)))
+		(if (member (cons variable val)
+                             (with-current-buffer buffer
+                               dir-local-variables-alist))
+		    (let ((file (and (buffer-file-name buffer)
+                                      (not (file-remote-p
+                                            (buffer-file-name buffer)))
                                       (dir-locals-find-file
-                                       (buffer-file-name))))
+                                       (buffer-file-name buffer))))
                           (dir-file t))
 		      (princ "  This variable's value is directory-local")
 		      (if (null file)