Justin had been so focused inward that he hadn't noticed anyone coming up behind him. He jumped a little at the voice and spun in surprise, his hand going to his chest where his heart raced at the scare. He relaxed, however, at the sight of Ernie, as for the slightest moment there, he'd thought it was someone's ghost there. Whose, he didn't know, but was more than happy not to find out.
"Hey, Ernie," he replied, trying for a grin to hide the scare he'd had. "Anyone ever tell you to knock before coming up on someone-" he looked around him. "Outside, in public?"
He slipped his hands into his pockets, feeling suddenly awkward as he hadn't seen his best mate since the night of the gala - since finding out Harry had died.