diff --git a/index.html b/index.html
index 5642806..edd1c5f 100644
--- a/index.html
+++ b/index.html
@@ -109,7 +109,7 @@ <h2>
         <pre class="idl"
 >partial interface MediaDevices {
   Promise&lt;MediaStream&gt; getViewportMedia(
-      optional DisplayMediaStreamConstraints constraints = {});
+      optional ViewportMediaStreamConstraints constraints = {});
 };</pre>
         <dl data-link-for="MediaDevices" data-dfn-for="MediaDevices" class="methods">
           <dt>
@@ -358,6 +358,49 @@ <h2 id="constrainable-properties">
         those relevant to {{MediaDevices/getDisplayMedia()}}, as defined in
         <a data-cite="SCREEN-CAPTURE#constrainable-properties">
           5.4 Constrainable Properties for Captured Display Surfaces</a>.
+        <section>
+          <h2>ViewportMediaStreamConstraints</h2>
+          <p>The <dfn>ViewportMediaStreamConstraints</dfn> dictionary is used to
+          instruct the user agent what sort of {{MediaStreamTrack}}s may be
+          included in the {{MediaStream}} returned by
+          {{MediaDevices/getViewportMedia}}.</p>
+          <div>
+            <pre class="idl">
+dictionary ViewportMediaStreamConstraints {
+  (boolean or MediaTrackConstraints) video = true;
+  (boolean or MediaTrackConstraints) audio = false;
+};</pre>
+            <section>
+              <h2>Dictionary <a class="idlType">ViewportMediaStreamConstraints</a>
+                Members</h2>
+              <dl data-link-for="ViewportMediaStreamConstraints" data-dfn-for=
+                "ViewportMediaStreamConstraints" class="dictionary-members">
+                <dt><dfn><code>video</code></dfn> of type <code>(boolean or {{MediaTrackConstraints}})</code>,
+                defaulting to <code>true</code></dt>
+                <dd>
+                  <p>If <code>true</code>, it requests that the returned
+                  {{MediaStream}} contain a video track. If a {{MediaTrackConstraints}}
+                  structure is provided, it further specifies desired processing
+                  options to be applied to the video track rendition of the
+                  display surface chosen by the user. If <code>false</code>, the
+                  request will be [=rejected=] with a {{TypeError}}, as per the
+                  {{MediaDevices/getViewportMedia}} algorithm</a>.</p>
+                </dd>
+                <dt><dfn><code>audio</code></dfn> of type <code>(boolean or {{MediaTrackConstraints}})</code>,
+                defaulting to <code>false</code></dt>
+                <dd>
+                  <p>If <code>true</code>, it signals an interest that the
+                  returned {{MediaStream}} contain an audio track, if
+                  supported and audio is available.
+                  If a {{MediaTrackConstraints}} structure is provided, it
+                  further specifies desired processing options to be applied to
+                  the audio track. If <code>false</code>, the {{MediaStream}}
+                  will not contain an audio track.</p>
+                </dd>
+              </dl>
+            </section>
+          </div>
+        </section>
       </section>
       <section data-cite="permissions">
         <h2 id="permissions-intergration">Permissions Integration</h2>