Post function "copy value from other field" does not work on create transition for Description field

Issue Summary

Post function "copy value from other field" does not work on the create transition for Description field when copying it from a text custom field

Steps to Reproduce

1. Navigate to your project settings > Workflows >Edit > Click on the create transition > Post functions
2. Configure the Post function "copy value from other field", copying the text custom field to the Description:                        
3. Save the workflow draft
4. Create an issue with any values in the text custom field

Expected Results

when creating a issue, the custom field value is added to the issue description.

Actual Results

The description is not set.

Workaround

None at this moment.