diff --git a/externs/managedmediasource.js b/externs/managedmediasource.js
index cca0dbd843..1c06840f19 100644
--- a/externs/managedmediasource.js
+++ b/externs/managedmediasource.js
@@ -22,3 +22,9 @@ function ManagedMediaSource() {}
  * @return {boolean}
  */
 ManagedMediaSource.isTypeSupported = function(type) {};
+
+/**
+ * @constructor
+ * @extends {SourceBuffer}
+ */
+function ManagedSourceBuffer() {}
diff --git a/lib/media/media_source_capabilities.js b/lib/media/media_source_capabilities.js
index eb0d0e0f80..63bf98a236 100644
--- a/lib/media/media_source_capabilities.js
+++ b/lib/media/media_source_capabilities.js
@@ -40,9 +40,10 @@ shaka.media.Capabilities = class {
    * @return {boolean}
    */
   static isChangeTypeSupported() {
-    return !!window.SourceBuffer &&
+    const sourceBuffer = window.ManagedSourceBuffer || window.SourceBuffer;
+    return !!sourceBuffer &&
         // eslint-disable-next-line no-restricted-syntax
-        !!SourceBuffer.prototype && !!SourceBuffer.prototype.changeType;
+        !!sourceBuffer.prototype && !!sourceBuffer.prototype.changeType;
   }
 };