Justify-content style is wrong for .ui-dialog-titlebar

Modal title bar is styled like this:

.ui-dialog-titlebar {
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-align: center;
  -ms-flex-align: center;
  align-items: center;
  -webkit-box-pack: justify;
  -ms-flex-pack: justify;
  justify-content: space-between;
  padding: 12px 1rem;
  border-bottom: 1px solid #e6e6e6;
}

This results is modal title text displaying at some distance from the left edge of the modal, which looks bad.

When justify-content is set to normal, the modal title aligns to the modal content.