Stefanow qualified for the 2017 Welsh Open and then saw off Michael Wild 4–3 to reach the second round, where he would go on to be comfortably defeated 1–4 by former World Champion Graeme Dott. He won his first round tie at 2018 World Championship qualifying 10–8 against Gary Wilson, before losing out 4–10 against Thepchaiya Un-Nooh.