material-web: md-dialog doesn't seem to work well with dark theme by default (pre.7)

Maybe there’s some trick to style it properly, but default is barely legible:

 <md-dialog id="terms-dialog" width="300">
        <div slot="header">
           ${msg('Terms and conditions')}
        </div>
        <p class="">
          ${msg(
          'By continuing, you agree to our Terms of Service and Privacy Policy.' }
        )}
        </p>
        <md-filled-button slot="footer" dialogAction="close">
          Cancel
        </md-filled-button>
        <md-filled-button
          id="confirm-button"
          slot="footer"
          @click=${this.handleAcceptTermsAndConditions}>
          ACCEPT
        </md-filled-button>
      </md-dialog>