diff --git a/src/components/ModalPortal.js b/src/components/ModalPortal.js
index 268fbd78..5f0e6b3f 100644
--- a/src/components/ModalPortal.js
+++ b/src/components/ModalPortal.js
@@ -379,6 +379,7 @@ export default class ModalPortal extends Component {
       onClick: this.handleContentOnClick,
       role: this.props.role,
       "aria-label": this.props.contentLabel,
+      "aria-modal": true,
       ...this.attributesFromObject("aria", this.props.aria || {}),
       ...this.attributesFromObject("data", this.props.data || {}),
       "data-testid": this.props.testId