# Compilation error while migration from 4.26.2 to 4.27.0

**URL:** <https://forums.unrealengine.com/t/compilation-error-while-migration-from-4-26-2-to-4-27-0/487863>\
**Category:** Platform & Builds\
**Tags:** error, engine-compile, unreal-engine, question\
**Created:** [August 23, 2021, 9:38pm UTC](https://forums.unrealengine.com/t/compilation-error-while-migration-from-4-26-2-to-4-27-0/487863 "2021-08-23T21:38:40Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![anonymous\_user\_8afed8c6](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_8afed8c6](https://forums.unrealengine.com/u/anonymous_user_8afed8c6)\
**Post date:** [August 23, 2021, 1:09pm UTC](https://forums.unrealengine.com/t/compilation-error-while-migration-from-4-26-2-to-4-27-0/487863/1 "2021-08-23T13:09:03Z")

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Resolved by adding following definition:

#define WIN32\_LEAN\_AND\_MEAN

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**Author:** ![anonymous\_user\_8afed8c6](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_8afed8c6](https://forums.unrealengine.com/u/anonymous_user_8afed8c6)\
**Post date:** [August 23, 2021, 9:38pm UTC](https://forums.unrealengine.com/t/compilation-error-while-migration-from-4-26-2-to-4-27-0/487863/2 "2021-08-23T21:38:40Z")

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While moving project to 4.27.0 version I got some complication errors which are not related to project source.

How to fix following issues?

C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(10326): error C4668: ‘\_WIN32\_WINNT\_WIN10\_TH2’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(10332): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS1’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(10337): error C4668: ‘\_WIN32\_WINNT\_WIN10\_TH2’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(10341): error C4668: ‘\_WIN32\_WINNT\_WIN10\_TH2’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(10348): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS2’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(10358): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS2’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(10362): error C4668: ‘\_WIN32\_WINNT\_WIN10\_TH2’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(10367): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS3’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(10374): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS4’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(10377): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS1’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(10380): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS4’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(10385): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS1’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(10388): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS5’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(10588): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS2’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(10612): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS5’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(14093): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS5’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(15406): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS2’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(15525): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS3’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(15675): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS4’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(15688): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS4’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’  
C:\Program Files (x86)\Windows Kits\10\include\10.0.19041.0\um\winioctl.h(15916): error C4668: ‘\_WIN32\_WINNT\_WIN10\_RS1’ is not defined as a preprocessor macro, replacing with ‘0’ for ‘#if/#elif’

Thank you

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<div class="post-metadata">

**Author:** ![BIBALLO1](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@BIBALLO1](https://forums.unrealengine.com/u/BIBALLO1)\
**Post date:** [September 4, 2021, 2:22pm UTC](https://forums.unrealengine.com/t/compilation-error-while-migration-from-4-26-2-to-4-27-0/487863/3 "2021-09-04T14:22:18Z")

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I’m having the same problem, where did you add the #define?

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**Author:** ![ASBMedia](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/asbmedia/32/888497_2.png) [@ASBMedia](https://forums.unrealengine.com/u/ASBMedia)\
**Post date:** [September 11, 2021, 7:50pm UTC](https://forums.unrealengine.com/t/compilation-error-while-migration-from-4-26-2-to-4-27-0/487863/4 "2021-09-11T19:50:50Z")

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Hi, I added it as “PublicDefinitions.Add(“WIN32\_LEAN\_AND\_MEAN”);” in MyPlugin.Build.cs file. Best of luck!

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**Author:** ![BIBALLO1](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@BIBALLO1](https://forums.unrealengine.com/u/BIBALLO1)\
**Post date:** [October 9, 2021, 11:35am UTC](https://forums.unrealengine.com/t/compilation-error-while-migration-from-4-26-2-to-4-27-0/487863/5 "2021-10-09T11:35:53Z")

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Yes, that way it works. Thank you : )

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**Author:** ![8nowf1ake](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@8nowf1ake](https://forums.unrealengine.com/u/8nowf1ake)\
**Post date:** [November 2, 2022, 6:20am UTC](https://forums.unrealengine.com/t/compilation-error-while-migration-from-4-26-2-to-4-27-0/487863/6 "2022-11-02T06:20:14Z")

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where did u find that myplugin.build.cs file T^T

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**Author:** ![lijunfeng717](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@lijunfeng717](https://forums.unrealengine.com/u/lijunfeng717)\
**Post date:** [July 26, 2024, 7:11am UTC](https://forums.unrealengine.com/t/compilation-error-while-migration-from-4-26-2-to-4-27-0/487863/7 "2024-07-26T07:11:38Z")

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> [@ASBMedia](#):
>
> PublicDefinitions.Add(“WIN32\_LEAN\_AND\_MEAN”);

Work for me, thank you !