Sirius' first inclination was to put off the matter for as long as possible - like, maybe til after one of them died, preferably Snape. But a moment's sober reflection - and a glance at Remus' sirius face - was enough to convince him that if twere done twere best done quickly. "Do you want to go now?" he asked cautiously, just on the chance that perhaps Remus didn't really wish to do it at this moment, and thus the matter would be postponed and he would be let off the hook.
But then it would be hanging over his head, and he didn't like that idea either. Sort of damned either way, wasn't he? "We could go to the library now and check?" he suggested, hoping that Madame Pince wasn't overly aggravated with him from the last time she'd run him and James out for being a bit boisterous in the stacks. Of course, setting off a dungbomb probably hadn't endeared either one of them to the stern librarian either, but it had been purely accidental, and not meant to be done there. Siriusly.
Sirius found that the memory of the event brought a smile to his face, which he quickly tried to hide from Remus, knowing that Remus had not found the situation at all amusing.