tab completion bug?

[TJ Luoma <luomat@xxxxxxxxx>]

I have these lines in my ~/.zshrc:

         db="${HOME}/Dropbox"

         sites="$db/sites"

If I type

         cd $db/

and press 'tab' I get a list of all of the directories in $db

BUT if I type

         cd $sites/

and press 'tab' I get

         cd $sites//Users/luomat/Dropbox/Sites/

Is this a bug or am I missing something? Because it seems like I
should be getting a list of directories in $sites/

ZSH_VERSION = 5.0.7 (Mac Homebrew compiled

(also happens in 5.0.5 -- the version bundled with OS X 10.10)

TjL