Audit with Google Chrome. Contrast ratio problem with btn btn-lg btn-primary btn-block

[ghost]

If I audit this page: https://getbootstrap.com/docs/4.0/examples/signin/

I receive in accessibility this warning:

Color Contrast Is Satisfactory
Screen readers and other assistive technologies require annotations to understand otherwise ambiguous content.

Background and foreground colors do not have a sufficient contrast ratio.
Low-contrast text is difficult or impossible for many users to read. Learn more.

View failing elements:

<button class="btn btn-lg btn-primary btn-block" type="submit">

[XhmikosR]

I have opened #23319 along time ago.

/CC @patrickhlauke