# Why this error occurs?

**URL:** <https://forums.unrealengine.com/t/why-this-error-occurs/427502>\
**Category:** Programming & Scripting\
**Tags:** unreal-engine\
**Created:** [June 16, 2018, 12:33pm UTC](https://forums.unrealengine.com/t/why-this-error-occurs/427502 "2018-06-16T12:33:17Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![tworiver](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@tworiver](https://forums.unrealengine.com/u/tworiver)\
**Post date:** [June 16, 2018, 12:33pm UTC](https://forums.unrealengine.com/t/why-this-error-occurs/427502/1 "2018-06-16T12:33:17Z")

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I just used `GetWordTimerManager().SetTimer()` and it says that it is an incomplete type that i used.  
Why this error occurs? And how can I fix this?  
(I’m korean, so my English can be little awkward)

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**Author:** ![Ali\_Akbar](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/ali_akbar/32/1008648_2.png) [@Ali\_Akbar](https://forums.unrealengine.com/u/Ali_Akbar)\
**Post date:** [June 17, 2018, 9:16am UTC](https://forums.unrealengine.com/t/why-this-error-occurs/427502/2 "2018-06-17T09:16:35Z")

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When you see errors like these (incomplete type), it means you’ll need to include the relevant header file

If you use the Visual Assist X plugin, right click on the SetTimer function and select “Add include”. Otherwise, you’ll have to manually find where the definition of GetWorldTimerManager is stored and include that file