Unknown type name ucontext64_t

Unknown type name 'ucontext64_t'; did you mean 'ucontext_t'?

What is the cause of this compilation error? Points to this code:

#ifdef __arm64__
    #define UC_MCONTEXT uc_mcontext64
    typedef ucontext64_t SignalUserContext;
#else
    #define UC_MCONTEXT uc_mcontext
    typedef ucontext_t SignalUserContext;
#endif

This code compiles in 1 of my projects, but it does not in the other. Both projects are linking to the same libraries. Anyone can help pointing to the build or other settings, which may affect that?