In this paper, we propose a new wavelength assignment scheme that improves the blocking probability of WDM networks that use limited-range wavelength converters. Limited-range wavelength converters are attractive for wavelength-routed networks given current technology since they offer good utilization of the wavelength resource and improved blocking probability. However, their conversion ranges are limited, the maximum difference between the input and output wavelengths is restricted. Thus, we must take into account the existence of these limitedrange wavelength converters. In our proposed scheme, each connection request is assigned a different wavelength according to its hop number. We tend to use different wavelengths for connection requests with different hop numbers. As a result, we can reduce the blocking probability by two decades compared to simply assigning the shortest available wavelengths. In addition, it allows the number of wavelength converters used in each node to be reduced with almost no degradation in blocking probability. Simulation results show that the proposed scheme can reduce the wavelength converters by about 20%.