# Loft Error

**URL:** <https://forum.dynamobim.com/t/loft-error/12877>\
**Category:** Geometry\
**Tags:** dynamo\
**Created:** [June 30, 2017, 4:37pm UTC](https://forum.dynamobim.com/t/loft-error/12877 "2017-06-30T16:37:29Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![zakazai](https://avatars.discourse-cdn.com/v4/letter/z/b4bc9f/32.png) [@zakazai](https://forum.dynamobim.com/u/zakazai)\
**Post date:** [June 30, 2017, 4:37pm UTC](https://forum.dynamobim.com/t/loft-error/12877/1 "2017-06-30T16:37:29Z")

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I was learning Dynamo,  
i tried an loft program, it worked fine, but i tried to make some changes and tried again then i get error message, even after i did it again.

Warning: Surface.ByLoft operation failed.  
Value cannot be null.  
Parameter name: source

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<div class="post-metadata">

**Author:** ![Azubike\_Ononye](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.dynamobim.com/azubike_ononye/32/23113_2.png) [@Azubike\_Ononye](https://forum.dynamobim.com/u/Azubike_Ononye)\
**Post date:** [June 30, 2017, 4:39pm UTC](https://forum.dynamobim.com/t/loft-error/12877/2 "2017-06-30T16:39:37Z")

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Hi please post a snapshot of your dynamo graph. Thanks.