Route rewriting length

[eluser]Unknown[/eluser]
Hi all,
I'm having a bit of trouble, I'm trying to do a custom route, I've done this...

'admin/([a-z]+)' => 'admin/area/$1'

The above works great for 'admin/something', 'admin/whatever', 'admin/etc'
However, if I just visit 'admin/' then it is also routing to 'admin/area/$1'

I've tried this...

'admin/([a-z]{1,}+)' => 'admin/area/$1'

But I get the same result.

Any suggestions
Thanks!