Controller failing to read flash

I’m seeing some pretty strange behavior from the flash in my rails
2.3.8 app. I set the flash in a request, and then redirect. In the
next request (the one redirected to), accessing the flash returns an
empty hash, but the flash is stored and visible in the session.

(rdb:21) session
{:user_credentials=>"…", :session_id=>"…", :user_credentials_id=>1,
status updated”}, :_csrf_token=>"…"}
(rdb:21) session[:flash]
{:notice=>“Twitter status updated”}
(rdb:21) flash

Looking at the source for flash in actionpack-2.3.8/lib/
the difference is that the key is stored as a string and not a symbol.
How could that disparity occur?

Access the contents of the flash. Use flash[“notice”] to

    # read a notice you put there or <tt>flash["notice"] =

# to put a new one.
def flash #:doc:
if !defined?(@_flash)
@_flash = session[“flash”] ||