diff --git a/lib/polyfill/encryption_scheme.js b/lib/polyfill/encryption_scheme.js
index 40ae224934..74b163e8ad 100644
--- a/lib/polyfill/encryption_scheme.js
+++ b/lib/polyfill/encryption_scheme.js
@@ -26,4 +26,4 @@ shaka.polyfill.EncryptionScheme = class {
 };
 
 // Install at a low priority so that other EME polyfills go first.
-shaka.polyfill.register(shaka.polyfill.EncryptionScheme.install, -1);
+shaka.polyfill.register(shaka.polyfill.EncryptionScheme.install, -2);
diff --git a/lib/polyfill/media_capabilities.js b/lib/polyfill/media_capabilities.js
index a97d02d37d..1dfde7ca3d 100644
--- a/lib/polyfill/media_capabilities.js
+++ b/lib/polyfill/media_capabilities.js
@@ -143,5 +143,6 @@ shaka.polyfill.MediaCapabilities = class {
   }
 };
 
-
-shaka.polyfill.register(shaka.polyfill.MediaCapabilities.install);
+// Install at a lower priority than MediaSource polyfill, so that we have
+// MediaSource available first.
+shaka.polyfill.register(shaka.polyfill.MediaCapabilities.install, -1);
diff --git a/lib/util/stream_utils.js b/lib/util/stream_utils.js
index 236b030f00..3c54229902 100644
--- a/lib/util/stream_utils.js
+++ b/lib/util/stream_utils.js
@@ -449,6 +449,7 @@ shaka.util.StreamUtils = class {
         const allCodecs = video.codecs.split(',');
         videoCodecs = shaka.util.ManifestParserUtils.guessCodecs(
             ContentType.VIDEO, allCodecs);
+        videoCodecs = shaka.util.StreamUtils.patchVp9(videoCodecs);
         const audioCodecs = shaka.util.ManifestParserUtils.guessCodecs(
             ContentType.AUDIO, allCodecs);
 
@@ -462,6 +463,7 @@ shaka.util.StreamUtils = class {
           spatialRendering: false,
         };
       }
+      videoCodecs = shaka.util.StreamUtils.patchVp9(videoCodecs);
       const fullType = shaka.util.MimeUtils.getFullOrConvertedType(
           video.mimeType, videoCodecs, ContentType.VIDEO);
       // VideoConfiguration
@@ -591,6 +593,21 @@ shaka.util.StreamUtils = class {
     return configs;
   }
 
+  /**
+   * MediaCapabilities supports 'vp09...' codecs, but not 'vp9'. Translate vp9
+   * codec strings into 'vp09...', to allow such content to play with
+   * mediaCapabilities enabled.
+   *
+   * @param {string} codec
+   * @return {string}
+   */
+  static patchVp9(codec) {
+    if (codec == 'vp9') {
+      return 'vp09.00.10.08';
+    }
+    return codec;
+  }
+
 
   /**
    * Alters the given Manifest to filter out any streams uncompatible with the
diff --git a/test/util/stream_utils_unit.js b/test/util/stream_utils_unit.js
index 455c9fb94c..c9249d7a83 100644
--- a/test/util/stream_utils_unit.js
+++ b/test/util/stream_utils_unit.js
@@ -633,6 +633,21 @@ describe('StreamUtils', () => {
           /* useMediaCapabilities= */ true);
       expect(manifest.variants.length).toBe(1);
     });
+
+    it('supports VP9 codec', async () => {
+      manifest = shaka.test.ManifestGenerator.generate((manifest) => {
+        manifest.addVariant(0, (variant) => {
+          variant.addVideo(1, (stream) => {
+            stream.mime('video/webm', 'vp9');
+          });
+        });
+      });
+
+      await shaka.util.StreamUtils.filterManifest(
+          fakeDrmEngine, /* currentVariant= */ null, manifest,
+          /* useMediaCapabilities= */ true);
+      expect(manifest.variants.length).toBe(1);
+    });
   });
 
   describe('chooseCodecsAndFilterManifest', () => {