How to use ICU's select with decimals on Symfony4?

Symfony4 uses ICU for translations. I want a rich display of time values in my translation - in French. For instance, 1.25 hours should display "One hour and a quarter" - pardon my french.

Yet, i found no way to escape dots, or wrap my "key" value with quotes. The following example always returns a U_PATTERN_SYNTAX_ERROR if i try any way of escaping the dot:

messages+intl-icu.fr.yml

  durationHours: >-
    {n, select,
        0     {Non précisé}
        1     {1 heure}
        1.25  {1 heure et quart}
        other {{n} heures}
    }

TaskService.php

$this->tl->trans('task.durationHours', ['n' => $task->getDurationInHours()]);

The docs i based my research upon:

• https://symfony.com/doc/current/translation/message_format.html#numbers
• http://userguide.icu-project.org/formatparse/messages#TOC-Quoting-Escaping