Whitespace not caught by Laravel validation

I'm trying to validate a password input field, and spaces are not getting caught by the validator. The password field should be a minimum of 6 characters, and the regex should allow spaces within a password, but not at the beginning or end (I've confirmed that this works outside of the validator).

When a user enters in 1+ spaces into the password field (but no other characters) and submits, the validator fails to catch it (i.e., " " isn't caught by the validator).

Here's what my validator looks like:

$this->validate($request, [
    'name' => 'required|max:255|alpha',
    'password' => 'http://regex:/^[^\s]+(\s+[^\s]+)*$/|min:6|confirmed',
]);

via Chebli Mohamed