nnvm/from_darknet llvm::BranchInst::AssertOK() problem

when I run nnvm/from_darknet.py , I use target = ‘llvm’, but error as follows:

lib/IR/Instructions.cpp:1130: void llvm::BranchInst::AssertOK(): Assertion `getCondition()->getType()->isIntegerTy(1) && “May only branch on boolean predicates!”’ failed.
Aborted (core dumped)

do i need to replace llvm version , i use llvm 6.0.1.