Can't push_back move(NonCopyable) to vector

I have a NonCopyable class (due to its unique_ptr field). I want to create a vector of NonCopyable elements but the following code wouldn't compile

    NonCopyable nc;
    vector<NonCopyable> vec;
    vec.push_back(move(nc));

The error message is Call to implicitly-deleted copy constructor of NonCopyable. Why doesn't the move optimization work in this case? How to fix it elegantly (without defining a copy constructor for NonCopyable)?

I'm using clang 6.0.