diff --git a/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-media/pageload-image.html b/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-media/pageload-image.html
index 1f9c084fd002fc..67c97bafddd5a9 100644
--- a/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-media/pageload-image.html
+++ b/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-media/pageload-image.html
@@ -14,6 +14,7 @@
   function frameLoaded() {
     var testframe = document.getElementById('testframe');
     assert_equals(testframe.contentDocument.contentType, "image/png");
+    assert_equals(testframe.contentDocument.compatMode, "CSS1Compat", "Media documents should be in standards mode");
     var testframeChildren = testframe.contentDocument.body.childNodes;
     assert_equals(testframeChildren.length, 1, "Body of image document has 1 child");
     assert_equals(testframeChildren[0].nodeName, "IMG", "Only child of body must be an <img> element");
diff --git a/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-media/pageload-video.html b/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-media/pageload-video.html
index 1ae414ceb6198c..9bce1f0c361a35 100644
--- a/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-media/pageload-video.html
+++ b/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-media/pageload-video.html
@@ -15,6 +15,7 @@
   var contentType = getMediaContentType(url);
   testframe.onload = this.step_func_done(function() {
     assert_equals(testframe.contentDocument.contentType, contentType);
+    assert_equals(testframe.contentDocument.compatMode, "CSS1Compat", "Media documents should be in standards mode");
     var testframeChildren = testframe.contentDocument.body.childNodes;
     assert_equals(testframeChildren.length, 1, "Body of image document has 1 child");
     assert_equals(testframeChildren[0].nodeName, "VIDEO", "Only child of body must be an <video> element");
diff --git a/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-text/load-text-plain-expected.txt b/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-text/load-text-plain-expected.txt
deleted file mode 100644
index aecbfdd7d97d15..00000000000000
--- a/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-text/load-text-plain-expected.txt
+++ /dev/null
@@ -1,6 +0,0 @@
-This is a testharness.js-based test.
-FAIL Checking document metadata for text file assert_equals: expected "BackCompat" but got "CSS1Compat"
-PASS Checking DOM for text file
-PASS Checking contents for text file
-Harness: the test ran to completion.
-
diff --git a/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-text/load-text-plain.html b/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-text/load-text-plain.html
index bd4fd78591f97f..ad7563153389b7 100644
--- a/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-text/load-text-plain.html
+++ b/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-text/load-text-plain.html
@@ -13,7 +13,7 @@
 iframe.onload = function(e) {
   var doc = iframe.contentDocument;
   t.step(function() {
-    assert_equals(doc.compatMode, "BackCompat");
+    assert_equals(doc.compatMode, "CSS1Compat");
     assert_equals(doc.contentType, "text/plain");
     assert_equals(doc.doctype, null);
     t.done();