Upgraded from WFFM 2.4 to 8.2u1. Forms that already exist is able to add new fields and edit in any way.

If i create a new form and try to press "Add field" in the form designer this error pops up:

enter image description here

Any ideas?

  • 1
    please, post the exception stacktrace as text, so that i could be googled in future Commented Jan 24, 2017 at 14:58

2 Answers 2


This is caused by a missing sub-item within the Web Forms for Marketers base form creation process. To fix this until Sitecore corrects the issue:

  1. Go into the Content Editor and find your Form
  2. Right click on your form and insert a new Form Section (or select it and use your insert options)
  3. Give it a name

That should get you working again. Until a fix is ready, I have created a basic form with just a "Fields" section and instead of creating a new form, I just click the button to copy from an existing form.

  • I made a branch template in wait for this to work, so that the section comes with the creation of a form. Thanks for the workaround tip! Commented Jan 25, 2017 at 8:24

Sitecore provided a support package for this issue. You can find it under https://kb.sitecore.net/articles/844911.

Just copy the Sitecore.Support.139810.config and the Sitecore.Support.139810.dll from the package to your servers and the issue should be fixed.

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