A working machine including a working assembly that can be driven by an engine, with the engine being connectable to the working assembly via a power branching transmission including a first mechanical power branch and a second electric or hydraulic power branch, the first and second power branches being combined by a summation transmission that can be coupled to the working assembly on the output side and provides a variable transmission ratio between the first mechanical power branch and the working assembly that can be adjusted by the rotational speed of the second electric or hydraulic power branch. A blocking device is provided for blocking the variability of the transmission ratio that can be adjusted between the first mechanical power branch and the output side of the summation transmission by the rotational speed of the second electric or hydraulic power branch.