* lisp/simple.el (shell-command-to-string):

Call `shell-command' in order to respect file name handlers.

lisp/simple.el

@@ -3844,7 +3844,7 @@ interactively, this is t."
   (with-output-to-string
     (with-current-buffer
       standard-output
-      (process-file shell-file-name nil t nil shell-command-switch command))))
+      (shell-command command t))))
 
 (defun process-file (program &optional infile buffer display &rest args)
   "Process files synchronously in a separate process.