Automation bug, or am I using it wrong?

I have an extractor that i want to turn off after an hour, so I set up this…

alias: Toilet Extractor off after 1 hour
description: ""
trigger:
  - platform: device
    type: turned_on
    device_id: 51df02baa7139319bfe8d5e30a9028fd
    entity_id: switch.toilet_extractor_switch
    domain: switch
    for:
      hours: 1
      minutes: 0
      seconds: 0
condition: []
action:
  - service: switch.turn_off
    data: {}
    target:
      entity_id: switch.toilet_extractor_switch
mode: single

Does not work, but if I set it to this

alias: Toilet Extractor off after 1 hour
description: ""
trigger:
  - platform: device
    type: turned_on
    device_id: 51df02baa7139319bfe8d5e30a9028fd
    entity_id: switch.toilet_extractor_switch
    domain: switch
    for:
      hours: 0
      minutes: 59
      seconds: 0
condition: []
action:
  - service: switch.turn_off
    data: {}
    target:
      entity_id: switch.toilet_extractor_switch
mode: single

It works… Any ideas why 1 hour wont turn the switch off?

Thanks.