LBlock is a 64-bit ultra-light block cipher suitable for the constrained environments such as wireless sensor network environments. In this paper, we propose a differential fault analysis on LBlock. Based on a random nibble fault model, our attack can recover the secret key of LBlock by using the exhaustive search of $2^{25}$ and five random nibble fault injection on average. It can be simulated on a general PC within a few seconds. This result is superior to known differential fault analytic result on LBlock.