Using "title" in jiralert.tmpl fails with wrong type for value; expected language.Tag; got string

[cjedro]

I´m currently trying to use title in the template but this fails with:

template: jiralert.tmpl:3:51: executing "jira.component" at <.GroupLabels.component>: wrong type for value; expected language.Tag; got string"

jiralert.tmpl

{{ define "jira.component" }}{{- .GroupLabels.component | title }}{{ end }}

jiralert.yml

template: jiralert.tmpl
defaults:
  api_url: https://xxx.atlassian.net
  description: "test"
  issue_type: Alert
  password: ""
  reopen_duration: 1h
  reopen_state: Reopening
  summary: "test"
  user: ""
  wont_fix_resolution: Won't Do

receivers:
  
  - name: 'jiralert-critical'
    project: 'OPS'
    add_group_labels: false
    priority: High
    fields:
      # Components
      components:
        - name: '{{ template "jira.component" . }}'

Am i missing something - looking at this line of code this should work, shouldn´t it?