Error Page is shown in wrong language

I’m not using any routes, language detection is on. Plugins I’m using are kirby3-xmlsitemap and uniform.
Language configurations:
DE
‘code’ => ‘de’,
‘default’ => true,
‘locale’ => ‘de_CH’,
‘name’ => ‘Deutsch’,
‘url’ => ‘/de’,
‘translations’ => […]

EN
‘code’ => ‘en’,
‘locale’ => ‘en_US’,
‘name’ => ‘English’,
‘url’ => ‘/en’,
‘translations’ => […]