We study the effect of the fragmentation of intellectual property rights on optimal patent design. The major finding is that when several complementary innovative components must be assembled to operate a new technology, the patentability requirements should be stronger than in the case of stand-alone innovation. This reduces the fragmentation of intellectual property, which is socially costly. However, to preserve the incentives to innovate,
if a patent is granted the strength of protection should be generally higher than in the stand-alone case.