Most existing mutual exclusion algorithms for mobile ad hoc networks (MANETs) adopt a token-based approach. In traditional wired networks, timeout-based mechanisms are commonly used to detect token losses. However, in MANETs, it is difficult to set a proper timeout value due to the network dynamics. In this paper, we propose a dual-token-based mutual exclusion algorithm, which can tolerate token losses without using timeout. Two tokens are concurrently circulated in the system to monitor each other by using sequence numbers. If one token is lost, the other token can detect the loss and regenerate a new token. Simulations have been carried out to evaluate the effectiveness and performance of the proposed algorithm in comparison with the timeout-based approach. The results show that the timeout-based algorithm may falsely claim the loss of a token, thus cannot guarantee the correctness of mutual exclusion algorithms. On the contrary, our proposed algorithm can avoid false detection of token losses and satisfy all the correctness requirements of mutual exclusion, though it costs a bit more messages and longer time.