Constants in path names not working since path

Since applying the 2016.1.1 patch, PHPStorm seems to be unable to resolve path names stored in constants.

So I can declare my path:

define("TEST_PATH", __DIR__ . "/test");

And PHPStorm will correctly autocomplete the "/test" folder part, not a problem, so it appears OK here. But, on the very next line, a require_once using this constant won't work and I'll get a "Path ... Not Found" message:

require_once(TEST_PATH . "/test.php");

If I try autocomplete the "/test.php" part, I get a "no suggestions" popup. Any ideas?

Cheers, Ben.