How to use ubsan with libFuzzer (on clang)?

I am currently getting started with fuzzing in C++. Following the tutorial at https://github.com/google/fuzzer-test-suite/blob/master/tutorial/libFuzzerTutorial.md I have successfully used the AddressSanitizer. In that tutorial it is also recommended to at least try UBSan as well.

The example from the documentation on UBSan work just fine, I immediatly get a runtime error because of the signed integer overflow. But when I try to build a fuzzer around the example I no longer get any errors reported.

The example code is

// test.cpp
int main(int argc, char **argv) {
    int k = 0x7fffffff;
    k += argc;
    return 0;
}

which I compiled with clang++ -fsanitize=undefined test.cpp -o test.

To get my fuzzer I changed the code to

// fuzz.cpp
#include <cstddef>

extern "C" int LLVMFuzzerTestOneInput(const char *data, size_t len)
{
    int k = 0x7fffffff;
    k += len;
    return 0;
}

and built it with clang++ -fsanitize=undefined -fno-sanitize-recover=undefined -fsanitize-coverage=trace-pc-guard fuzz.cpp libFuzzer.a -o fuzz.

Does any one know what I have to change, so that the fuzzer also finds the signed integer overflow?