The processes that guide performance in Wason's selection task (WST) are still under debate. The matching bias effect in the negations paradigm and its elimination by explicit negations are central arguments against a substantial role for inferential processes. Two WST experiments were conducted in the negations paradigm to replicate the basic finding and to compare effects of implicit and explicit negations. Results revealed robust matching bias in implicit negations. In contrast to previous findings, matching bias was reduced but not eliminated in conditions using explicit negations. Model-based analyses suggest that matching bias is due to a switch towards a negative test strategy caused by negations.