I couldn't find one - so I added a correction bone between the feet.
Then I added keyframes for this bone to make the model walk in place. It seems to be a rather common practice.
You can also try to modify existing keyframes of the root bone, but this can be annoying when there are many keyframes available, as you have to adjust each and every of them. With a correction bone you usually get away with less.
You can correct either in the 3d view, which can be tedious or you might want to try Blender's curve editor which displays all changes to bones and their properites (xyxz pos, rotation,...) as lines.... similar to the Unity animation curve editor.

That's the fine tuning which has to be done for nearly every animation. Especially walk and run, as capturing a walk in place aniamtion will deliver rather unrealistic results.