MAILPATH stopped working after update to Bash 4.0

[Nikos Chantziaras]

I have:

  MAILPATH="/home/me/.maildir/new?You have new mail."
  MAILCHECK=60

Bash 3.2 was correctly telling me about new mail arriving.  However, 
after I updated to Bash 4.0, I constantly get a "You have new mail." 
message every minute even though I actually don't have new mail.  Has 
the mail notification feature changed in Bash 4.0?  I can't see anything 
relevant in the man page or NEWS file.