Convert 4.9.1 project to 4.8 fails


I have a project in 4.9.1 and I am developing for VR, with a rush to finish the project in a couple of weeks, but 4.9.1 is useless for VR right now, so I have attempted to migrate the project from 4.9.1 to 4.8 with no success.

I have installed version 4.8.3, created a blank project, and then I have used Migrate of all Content folder in 4.9.1 project. The assets are copied ok, but when I open the 4.8 project, Unreal gives me this message:

Failed to load map!
.umap is a UE4 map [File:v482], from an engine release newer than this [Cur:v451]

I have checked the About box and my version is 4.8.3, so I do not understand why the umap file isn’t compatible and say current version is 4.5.1.

Any idea of what is wrong with this migration?

Any help will be appreciated because we are in a big struggle trying to finish the project.


Thats very weird. Have you tried manually copying the whatever.umap from the 4.9.1 project to the 4.8.x project under the same folder structure? (youll probably have a bunch of missing references to fix but at least it will tell you if its the migration or not)

When you migrated did you get a “Migration completed succesfully xxx files copied” or did you get “some files were not copied”

Are you gamemodes set properly, gameinstance class, any C++ classes etc. what about plugins did you use any plugins youd need the old versions.

Hope this helps
Don’t forget to accept an answer that best clears your question up or answers it so when the community finds your question in the future via search/google they know exactly what you did to fix it/get it going.

Usually there is a possibility of evolution but not regress, and common sense that it is not possible.
Let’s see, who command although it may have identical characteristics can not be, can be designed to interact differently in that the previous version did not exist, so the possibility of regress is not possible, you will not find parallelism in this version, because in previous version did not include and had not been thought that option / feature.
But somebody else to manifest, but I think it is something similar …

Council: create copies of projects in stages and each time gives a gentler pace, always have your backup.