REST API - getting unknown property by sequence flow after trying to complete form

Hi Guys,

I am testing out the condition expression for the sequence flow and
I set the condition expression to check the outcome of the form:

When I try to complete the form via the task REST API, I am getting the following error:

{

"message": "Internal server error",

"exception": "Unknown property used in expression: ${form_review_outcome == \"Approve\"}"

}

my request is the following:

{

“action”: “complete”,

“assignee”: “admin”,

“formId”: “30d91c47-02f5-11eb-9f1a-0a58a9feac2a”,

“outcome”: “Approve”
}

I am able to complete the form successfully via process-task but not via REST API. Appreciate any advice on what I might have done incorrectly.

Thank you!