Epiclink in Invoke-RestMehod

hi,

I’m doing Rest calls into Jira and after the field reference to add a story to an epic via epic link

using following as -Body of request, i assume my epiclink field is not correct
$global:IssueCreationBody =
@{
fields = @{
project = @{ key = $projectKey }
summary = $summary
description = $description
issuetype = @{ id = ‘51’ }#this is a story issuetype }
assignee = @{ name = $username }
priority = @{ id = ‘3’ }#no priority }
epiclink = @{ key = ‘CNS-3552’ }
}
} | ConvertTo-Json -Depth 100

response failure is “Error: The remote server returned an error: (400) Bad Request…Exception.Message” which tells me the body is malformed
any quick reference appreciated.