diff --git a/content/media/mediasource/SourceBuffer.cpp b/content/media/mediasource/SourceBuffer.cpp
index e6570b772a0d..57fe1f586470 100644
--- a/content/media/mediasource/SourceBuffer.cpp
+++ b/content/media/mediasource/SourceBuffer.cpp
@@ -289,7 +289,15 @@ void
 SourceBuffer::StopUpdating()
 {
   MOZ_ASSERT(NS_IsMainThread());
-  MOZ_ASSERT(mUpdating);
+  if (!mUpdating) {
+    // The buffer append algorithm has been interrupted by abort().
+    //
+    // If the sequence appendBuffer(), abort(), appendBuffer() occurs before
+    // the first StopUpdating() runnable runs, then a second StopUpdating()
+    // runnable will be scheduled, but still only one (the first) will queue
+    // events.
+    return;
+  }
   mUpdating = false;
   QueueAsyncSimpleEvent("update");
   QueueAsyncSimpleEvent("updateend");
diff --git a/testing/web-platform/meta/media-source/SourceBuffer-abort-updating.html.ini b/testing/web-platform/meta/media-source/SourceBuffer-abort-updating.html.ini
index be478219659e..84262857e64d 100644
--- a/testing/web-platform/meta/media-source/SourceBuffer-abort-updating.html.ini
+++ b/testing/web-platform/meta/media-source/SourceBuffer-abort-updating.html.ini
@@ -1,9 +1,5 @@
 [SourceBuffer-abort-updating.html]
   type: testharness
-  expected: ERROR
-  [SourceBuffer#abort() (video/webm; codecs="vorbis,vp8") : Check the algorithm when the updating attribute is true.]
-    expected: FAIL
-
   [SourceBuffer#abort() (video/mp4) : Check the algorithm when the updating attribute is true.]
     expected: FAIL