CheckbBox setUncheckedValue() does not appear as hidden input, if checkbox was initially disabled

Steps to reproduce:

1. Go to Administration->Authentication->SAML settings
2. Inspect Sign Messages checkbox using Chrome Inspect tool.
3. Observed: input type hidden with value=0 does not appear. Input type checkbox is disabled.
4. Click "Enable SAML authentication" checkbox checked.

Result:

Sign Messages checkbox inspect shows Input type checkbox enabled, new input type hidden does not appear.
Expected:
Sign Messages checkbox input type checkbox should be enabled and new input type hidden with unchecked value should appear.