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

goroutine 23 [running]:
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000453200?}, {0xe56770?, 0xc000453480?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:377 +0x425
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000453180?}, {0xe56770?, 0xc000453400?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000453100?}, {0xe56770?, 0xc000453380?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc0004530e0?}, {0xe56770?, 0xc000453360?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc0004530c0?}, {0xe56770?, 0xc000453340?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc0004530a0?}, {0xe56770?, 0xc000453320?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000453080?}, {0xe56770?, 0xc000453300?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000453060?}, {0xe56770?, 0xc0004532e0?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.replaceArg({0xe56770?, 0xc000453040?}, {0xe56770?, 0xc0004532c0?})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/prog.go:382 +0x345
github.com/google/syzkaller/prog.(*StructType).mutate(0x16d4620, 0xc000453280, 0xc00c5643c0, {0xe56770, 0xc000453020?}, {0xc00c564238, {0x1db7580, 0x4, 0x4}, 0xc00ce419e0, ...})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:490 +0x185
github.com/google/syzkaller/prog.(*Target).mutateArg(0x418408?, 0xc000240f60?, 0xc0000e7dc8?, {0xe56770, 0xc000453020}, {0xc00c564238, {0x1db7580, 0x4, 0x4}, 0xc00ce419e0, ...}, ...)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:245 +0xe2
github.com/google/syzkaller/prog.(*mutator).mutateArg(0xc0000e7e48)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:196 +0x245
github.com/google/syzkaller/prog.(*Prog).Mutate(0xc00caf6b00, {0xe52aa8?, 0xc00173e4e0}, 0x1e, 0xc00130e000, 0xc000112d20, {0xc00141e000, 0x41f, 0x500})
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:51 +0x2ba
main.(*Proc).loop(0xc00130e080)
	/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