"Use of undefined constant UC_SAGEPAYSERVER_SIMULATOR_URL" and three others

We recently updated PHP on our development server to version 5.3.6. It's now throwing notices for lines 5, 6 and 7 in uc_sagepayserver.module. This is because the three constants defined on this line are named by assumption rather than strings.

Not sure if this just different settings our side or a change in PHP; I couldn't see it mentioned in PHP's changelog. Regardless, I don't see why these constants' names are not defined as strings.