RuntimeException when extracting artisan key

[SilentDecode]

When I followed the guide exactly as you mentioned on your site, with of course some changes in terms of passwords and such.
Now with the last step in getting Firefly to work, I get an error with extracting the key.

~/firefly$ docker compose exec app php artisan key:generate --show

RuntimeException

Unsupported cipher or incorrect key length. Supported ciphers are: aes-128-cbc, aes-256-cbc, aes-128-gcm, aes-256-gcm.

at vendor/laravel/framework/src/Illuminate/Encryption/Encrypter.php:61
57▕
58▕ if (! static::supported($key, $cipher)) {
59▕ $ciphers = implode(', ', array_keys(self::$supportedCiphers));
60▕
➜ 61▕ throw new RuntimeException("Unsupported cipher or incorrect key length. Supported ciphers are: {$ciphers}.");
62▕ }
63▕
64▕ $this->key = $key;
65▕ $this->cipher = $cipher;

  +24 vendor frames 

25 app/Exceptions/Handler.php:231
Illuminate\Auth\AuthManager::__call()
+3 vendor frames

29 artisan:35
Illuminate\Foundation\Console\Kernel::handle()

~/firefly$