Cathal had been frowning at her words, especially I couldn't wait, but when she praised his work it drew Cathal back and away (a little) from his worries. He didn't want to make Marcie talk about anything before she wanted to.
"Ah, cheers, I'm glad to hear it," Cathal grinned. "Though I hope it doesn't turn out you got stranded here cause of a part I rebuilt."