panic: replaceArg: group fields don't match: 0/1

goroutine 16 [running]:
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000b5e240?}, {0xe56770?, 0xc000b5e460?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:377 +0x425
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000b5e220?}, {0xe56770?, 0xc000b5e440?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000b5e200?}, {0xe56770?, 0xc000b5e420?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000b5e1e0?}, {0xe56770?, 0xc000b5e400?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000b5e140?}, {0xe56770?, 0xc000b5e360?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000b5e120?}, {0xe56770?, 0xc000b5e340?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000b5e100?}, {0xe56770?, 0xc000b5e320?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000b5e0e0?}, {0xe56770?, 0xc000b5e300?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000b5e0c0?}, {0xe56770?, 0xc000b5e2e0?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000b5e0a0?}, {0xe56770?, 0xc000b5e2c0?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000b5e080?}, {0xe56770?, 0xc000b5e2a0?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.(*StructType).mutate(0x16d44a0, 0xc000b5e260, 0xc00bbd47d0, {0xe56770, 0xc000b5e060?}, {0xc00bbd4788, {0x1db72e0, 0x4, 0x4}, 0xc00bbd1350, ...})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:490 +0x185
github.com/google/syzkaller/prog.(*Target).mutateArg(0x418408?, 0xc000624340?, 0xc000cc7dc8?, {0xe56770, 0xc000b5e060}, {0xc00bbd4788, {0x1db72e0, 0x4, 0x4}, 0xc00bbd1350, ...}, ...)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:245 +0xe2
github.com/google/syzkaller/prog.(*mutator).mutateArg(0xc000cc7e48)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:196 +0x245
github.com/google/syzkaller/prog.(*Prog).Mutate(0xc00bbf6f40, {0xe52aa8?, 0xc000bb9020}, 0x1e, 0xc001410000, 0xc000551140, {0xc000556000, 0x55a, 0x700})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:51 +0x2ba
main.(*Proc).loop(0xc0011c0e00)
	/syzkaller/gopath/src/github.com/google/syzkaller/syz-fuzzer/proc.go:95 +0x365
created by main.main in goroutine 1
	/syzkaller/gopath/src/github.com/google/syzkaller/syz-fuzzer/fuzzer.go:336 +0x1665