Trouble migrating C++ project from 4.13.2 to 4.15.1

Installed 4.15.1 and tried to open my project. It asked to copy the project over and re-compile it. This was the result:

Project files could not be generated. Log output:

Running C:/Program Files/Epic Games/UE_4.15/Engine/Binaries/DotNET/UnrealBuildTool.exe -projectfiles -project=“C:/Users/Ghengis Khan/Documents/Unreal Projects/MyProject 4.15/MyProject.uproject” -game -rocket -progress

Discovering modules, targets and source code for project…

Messages while compiling C:\Users\Ghengis Khan\Documents\Unreal Projects\MyProject 4.15\Intermediate\Build\BuildRules\MyProjectModuleRules.dll:
c:\Users\Ghengis Khan\Documents\Unreal Projects\MyProject 4.15\Source\MyProject.Target.cs(35,48) : error CS0115: ‘MyProjectTarget.GUBP_GetPlatforms_MonolithicOnly(UnrealBuildTool.UnrealTargetPlatform)’: no suitable method found to override

UnrealBuildTool Exception: ERROR: UnrealBuildTool encountered an error while compiling source files