Bit-field with std::byte as member type cannot be initialized: bug or feature?

[Klaus Doldinger]

In C++20 bit-field initializer are possible. But this feature seems
impossible to use with std::byte.

struct Test {
    std::byte a : 2 = std::byte{0}; // NOK
    uint8_t   b : 2 = 0; // OK
};

Is this intentional or a bug in g++-10 (the version I'm using).

Thanks,
 Wilhelm