diff --git a/testing/web-platform/meta/media-source/mediasource-config-change-mp4-a-bitrate.html.ini b/testing/web-platform/meta/media-source/mediasource-config-change-mp4-a-bitrate.html.ini
index 6547fa045efb..bac178b41b5d 100644
--- a/testing/web-platform/meta/media-source/mediasource-config-change-mp4-a-bitrate.html.ini
+++ b/testing/web-platform/meta/media-source/mediasource-config-change-mp4-a-bitrate.html.ini
@@ -1,3 +1,5 @@
 [mediasource-config-change-mp4-a-bitrate.html]
   type: testharness
-  disabled: https://bugzilla.mozilla.org/show_bug.cgi?id=1066467
+  [Tests mp4 audio-only bitrate changes.]
+    expected: FAIL
+
diff --git a/testing/web-platform/meta/media-source/mediasource-config-change-mp4-av-audio-bitrate.html.ini b/testing/web-platform/meta/media-source/mediasource-config-change-mp4-av-audio-bitrate.html.ini
index 45fd4061d110..68ddfa906b57 100644
--- a/testing/web-platform/meta/media-source/mediasource-config-change-mp4-av-audio-bitrate.html.ini
+++ b/testing/web-platform/meta/media-source/mediasource-config-change-mp4-av-audio-bitrate.html.ini
@@ -1,3 +1,5 @@
 [mediasource-config-change-mp4-av-audio-bitrate.html]
   type: testharness
-  disabled: https://bugzilla.mozilla.org/show_bug.cgi?id=1066467
+  [Tests mp4 audio bitrate changes in multiplexed content.]
+    expected: FAIL
+
diff --git a/testing/web-platform/meta/media-source/mediasource-config-change-mp4-av-framesize.html.ini b/testing/web-platform/meta/media-source/mediasource-config-change-mp4-av-framesize.html.ini
index 655e637ade00..47c5d53465b5 100644
--- a/testing/web-platform/meta/media-source/mediasource-config-change-mp4-av-framesize.html.ini
+++ b/testing/web-platform/meta/media-source/mediasource-config-change-mp4-av-framesize.html.ini
@@ -1,3 +1,5 @@
 [mediasource-config-change-mp4-av-framesize.html]
   type: testharness
-  disabled: https://bugzilla.mozilla.org/show_bug.cgi?id=1066467
+  [Tests mp4 frame size changes in multiplexed content.]
+    expected: FAIL
+
diff --git a/testing/web-platform/meta/media-source/mediasource-config-change-mp4-av-video-bitrate.html.ini b/testing/web-platform/meta/media-source/mediasource-config-change-mp4-av-video-bitrate.html.ini
index 7b58fc5a8a0c..37d35deae582 100644
--- a/testing/web-platform/meta/media-source/mediasource-config-change-mp4-av-video-bitrate.html.ini
+++ b/testing/web-platform/meta/media-source/mediasource-config-change-mp4-av-video-bitrate.html.ini
@@ -1,3 +1,5 @@
 [mediasource-config-change-mp4-av-video-bitrate.html]
   type: testharness
-  disabled: https://bugzilla.mozilla.org/show_bug.cgi?id=1066467
+  [Tests mp4 video bitrate changes in multiplexed content.]
+    expected: FAIL
+
diff --git a/testing/web-platform/meta/media-source/mediasource-config-change-mp4-v-bitrate.html.ini b/testing/web-platform/meta/media-source/mediasource-config-change-mp4-v-bitrate.html.ini
index 728d83f02f94..d4f30e02e1da 100644
--- a/testing/web-platform/meta/media-source/mediasource-config-change-mp4-v-bitrate.html.ini
+++ b/testing/web-platform/meta/media-source/mediasource-config-change-mp4-v-bitrate.html.ini
@@ -1,3 +1,5 @@
 [mediasource-config-change-mp4-v-bitrate.html]
   type: testharness
-  disabled: https://bugzilla.mozilla.org/show_bug.cgi?id=1066467
+  [Tests mp4 video-only bitrate changes.]
+    expected: FAIL
+
diff --git a/testing/web-platform/meta/media-source/mediasource-config-change-mp4-v-framerate.html.ini b/testing/web-platform/meta/media-source/mediasource-config-change-mp4-v-framerate.html.ini
index a3e998d35746..7fcf76f9e170 100644
--- a/testing/web-platform/meta/media-source/mediasource-config-change-mp4-v-framerate.html.ini
+++ b/testing/web-platform/meta/media-source/mediasource-config-change-mp4-v-framerate.html.ini
@@ -1,3 +1,5 @@
 [mediasource-config-change-mp4-v-framerate.html]
   type: testharness
-  disabled: https://bugzilla.mozilla.org/show_bug.cgi?id=1066467
+  [Tests mp4 video-only frame rate changes.]
+    expected: FAIL
+
diff --git a/testing/web-platform/meta/media-source/mediasource-config-change-mp4-v-framesize.html.ini b/testing/web-platform/meta/media-source/mediasource-config-change-mp4-v-framesize.html.ini
index a8beb3268c31..37d1e217409f 100644
--- a/testing/web-platform/meta/media-source/mediasource-config-change-mp4-v-framesize.html.ini
+++ b/testing/web-platform/meta/media-source/mediasource-config-change-mp4-v-framesize.html.ini
@@ -1,3 +1,5 @@
 [mediasource-config-change-mp4-v-framesize.html]
   type: testharness
-  disabled: https://bugzilla.mozilla.org/show_bug.cgi?id=1066467
+  [Tests mp4 video-only frame size changes.]
+    expected: FAIL
+