🚀 go-pugleaf

I can't seem to make a buffer local variable stick
in the minibuffer.  It seems as though the first time
I read from the minibuffer, the variable goes back
to its global binding.  Is this a bug, or a feature,
or am I doing something dumb?  Thanks in advance.

Example:
(save-excursion (set-buffer " *Minibuf-0*")
		(symbol-value 'meta-prefix-char))
=>27

(save-excursion (set-buffer " *Minibuf-0*")
		(make-variable-buffer-local 'meta-prefix-char)
		(setq meta-prefix-char 28))
=>28

(save-excursion (set-buffer " *Minibuf-0*")
		(symbol-value 'meta-prefix-char))
=>28

(read-string "Foo ")	; read from the minibuffer
=>"bar"

(save-excursion (set-buffer " *Minibuf-0*")
		(symbol-value 'meta-prefix-char))
=>27