1. Go to Special:Block
2. Enter a target and select 'other time' in expiry field.
3. Submit the form.
4. You'll see a "This value is required" error next to expiry field.
5. Now select an actual expiry time from the dropdown menu.

Actual: The error is still there even when you select the expiry.
Expected: The error should go away once you select the expiry.