Upgraded from roots to sage and now have an error in functions.oho

Upon upgrading from the roots theme to sage (which now requires at least php 5.4), it's giving me an error:

Parse error: syntax error, unexpected '[' in .../functions.php on line 12

The server is updated to 5.5.21 and not sure what's going on. I've changed that code to the previous method for an array and it works (but this problem exists elsewhere). Any idea as to why this is happening?