Customizing include & can only have type 'structure'

What causes this issue?

Prefix 'CI_' is reserved for customizing includes.
Customizing includes are used to extend SAP structures and
tables. These are simply field definitions which do not conain any
data. The include therefore can only be created as a structure.

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

System Response

How to fix this error?

Create the customizing include as a structure.

Error message extract from SAP system. Copyright SAP SE.