Wolves halted a run of four successive defeats via last weekend's 3-2 home success over Sunderland. But they remain in the bottom three and McCarthy knows they have to tighten up at the back.
He said: "Last weekend was just reward for the work we have put in. We played well, got that little bit of luck and want to build on it.
"But we need to keep a clean sheet and not concede the type of goals we have been doing.
"The win over Sunderland was the first time we have scored three times at home in the Premier League. But we can't afford to concede two goals because we aren't going to win too many matches 3-2."
Source: PA
Source: PA