Bug: When adding media query CSS in Hustle

When adding media query in Hustle Custom CSS in for Custom Content, is breaking the CSS design.

For eg:

@media only screen and (max-width: 767px) {
.wph-modal.wph-modal--simple .wph-modal--content {
display: block;
}
.wph-modal .wph-modal--close {
text-align: center;
}
}