diff --git a/lib/ads/interstitial_ad_manager.js b/lib/ads/interstitial_ad_manager.js
index 91c1f3707f..1fba90c5a8 100644
--- a/lib/ads/interstitial_ad_manager.js
+++ b/lib/ads/interstitial_ad_manager.js
@@ -39,6 +39,9 @@ shaka.ads.InterstitialAdManager = class {
    * @param {function(!shaka.util.FakeEvent)} onEvent
    */
   constructor(adContainer, basePlayer, baseVideo, onEvent) {
+    /** @private {?shaka.extern.AdsConfiguration} */
+    this.config_ = null;
+
     /** @private {HTMLElement} */
     this.adContainer_ = adContainer;
 
@@ -197,11 +200,26 @@ shaka.ads.InterstitialAdManager = class {
    * @param {shaka.extern.AdsConfiguration} config
    */
   configure(config) {
-    if (!this.adContainer_ ||
-        this.usingBaseVideo_ != config.supportsMultipleMediaElements) {
+    this.config_ = config;
+  }
+
+  /**
+   * @private
+   */
+  determineIfUsingBaseVideo_() {
+    if (!this.adContainer_ || !this.config_ || this.playingAd_) {
+      return;
+    }
+    let supportsMultipleMediaElements =
+        this.config_.supportsMultipleMediaElements;
+    const video = /** @type {HTMLVideoElement} */(this.baseVideo_);
+    if (video.webkitSupportsFullscreen && video.webkitDisplayingFullscreen) {
+      supportsMultipleMediaElements = false;
+    }
+    if (this.usingBaseVideo_ != supportsMultipleMediaElements) {
       return;
     }
-    this.usingBaseVideo_ = !config.supportsMultipleMediaElements;
+    this.usingBaseVideo_ = !supportsMultipleMediaElements;
     if (this.usingBaseVideo_) {
       this.video_ = this.baseVideo_;
       if (this.adVideo_) {
@@ -491,6 +509,7 @@ shaka.ads.InterstitialAdManager = class {
    */
   async setupAd_(interstitial, sequenceLength, adPosition, initialTime,
       oncePlayed = 0) {
+    this.determineIfUsingBaseVideo_();
     goog.asserts.assert(this.video_, 'Must have video');
 
     this.lastPlayedAd_ = interstitial;
@@ -618,6 +637,7 @@ shaka.ads.InterstitialAdManager = class {
             this.baseVideo_.play();
           }
         }
+        this.determineIfUsingBaseVideo_();
       }
     };
     const error = async (e) => {