alerts (and maybe other components) broken

The css of alerts (e.g. alert-danger) looks like the following:

.alert-danger {
    color: white;
    background-color: white;
    border-color: white;
}

It should looks like:

.alert-danger {
    color: #721c24;
    background-color: #f8d7da;
    border-color: #f5c6cb;
}

This happened after we started generating our own botostrap css.