Oxford United have joined Coventry City and Wycombe Wanderers in the semi-final of the EFL Trophy.
In their Quarter-Final with Bradford City, former City loanee Chris McGuire scored a 53rd minute penalty with Johnson adding a second two minutes later.
Bradford City had former City midfielder Romain Vincelot booked before Hiwula-Mayifuila set up a grandstand finish with a goal in the 85th minute.
Oxford held on to win 2-1 and will now face Luton or Yeovil in the semi-final.