diff --git a/core/modules/update/tests/modules/update_test/aaa_update_test.1_0.xml b/core/modules/update/tests/modules/update_test/aaa_update_test.1_0.xml
index 55234d6b5f..8f710f7173 100644
--- a/core/modules/update/tests/modules/update_test/aaa_update_test.1_0.xml
+++ b/core/modules/update/tests/modules/update_test/aaa_update_test.1_0.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.x-1.</recommended_branch>
 <supported_branches>8.x-1.</supported_branches>
-<default_major>1</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/aaa_update_test</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-1.1_8.x-1.2.xml b/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-1.1_8.x-1.2.xml
index 4757b868e8..a29501cec7 100644
--- a/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-1.1_8.x-1.2.xml
+++ b/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-1.1_8.x-1.2.xml
@@ -6,7 +6,6 @@
  <api_version>8.x</api_version>
  <recommended_branch>8.x-1.</recommended_branch>
  <supported_branches>8.x-1.</supported_branches>
- <default_major>1</default_major>
  <project_status>published</project_status>
  <link>http://example.com/project/aaa_update_test</link>
  <terms>
diff --git a/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-1.2.xml b/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-1.2.xml
index cc16345b97..42f305fac6 100644
--- a/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-1.2.xml
+++ b/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-1.2.xml
@@ -6,7 +6,6 @@
  <api_version>8.x</api_version>
  <recommended_branch>8.x-1.</recommended_branch>
  <supported_branches>8.x-1.</supported_branches>
- <default_major>1</default_major>
  <project_status>published</project_status>
  <link>http://example.com/project/aaa_update_test</link>
  <terms>
diff --git a/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-1.2_8.x-2.2.xml b/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-1.2_8.x-2.2.xml
index df41223f2d..3248bb500b 100644
--- a/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-1.2_8.x-2.2.xml
+++ b/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-1.2_8.x-2.2.xml
@@ -6,7 +6,6 @@
  <api_version>8.x</api_version>
  <recommended_branch>8.x-2.</recommended_branch>
  <supported_branches>8.x-1.,8.x-2.</supported_branches>
- <default_major>2</default_major>
  <project_status>published</project_status>
  <link>http://example.com/project/aaa_update_test</link>
  <terms>
diff --git a/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-2.2_1.x_secure.xml b/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-2.2_1.x_secure.xml
index 9ac3eda36f..403d73d4aa 100644
--- a/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-2.2_1.x_secure.xml
+++ b/core/modules/update/tests/modules/update_test/aaa_update_test.sec.8.x-2.2_1.x_secure.xml
@@ -6,7 +6,6 @@
  <api_version>8.x</api_version>
  <recommended_branch>8.x-2.</recommended_branch>
  <supported_branches>8.x-1.,8.x-2.</supported_branches>
- <default_major>2</default_major>
  <project_status>published</project_status>
  <link>http://example.com/project/aaa_update_test</link>
  <terms>
diff --git a/core/modules/update/tests/modules/update_test/bbb_update_test.1_0.xml b/core/modules/update/tests/modules/update_test/bbb_update_test.1_0.xml
index be70b85b58..1a537d1563 100644
--- a/core/modules/update/tests/modules/update_test/bbb_update_test.1_0.xml
+++ b/core/modules/update/tests/modules/update_test/bbb_update_test.1_0.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.x-1.</recommended_branch>
 <supported_branches>8.x-1.</supported_branches>
-<default_major>1</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/bbb_update_test</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/ccc_update_test.1_0.xml b/core/modules/update/tests/modules/update_test/ccc_update_test.1_0.xml
index 35b3976b04..ce0d5aafac 100644
--- a/core/modules/update/tests/modules/update_test/ccc_update_test.1_0.xml
+++ b/core/modules/update/tests/modules/update_test/ccc_update_test.1_0.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.x-1.</recommended_branch>
 <supported_branches>8.x-1.</supported_branches>
-<default_major>1</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/ccc_update_test</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.0.0-alpha1.xml b/core/modules/update/tests/modules/update_test/drupal.0.0-alpha1.xml
index fbd3f3dadd..edb6187884 100644
--- a/core/modules/update/tests/modules/update_test/drupal.0.0-alpha1.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.0.0-alpha1.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.0.0-beta1.xml b/core/modules/update/tests/modules/update_test/drupal.0.0-beta1.xml
index 5f3dfdde2b..db84144c18 100644
--- a/core/modules/update/tests/modules/update_test/drupal.0.0-beta1.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.0.0-beta1.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.0.0.xml b/core/modules/update/tests/modules/update_test/drupal.0.0.xml
index a480482f20..bdf18b2e82 100644
--- a/core/modules/update/tests/modules/update_test/drupal.0.0.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.0.0.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.0.1-alpha1.xml b/core/modules/update/tests/modules/update_test/drupal.0.1-alpha1.xml
index 8d227e1eb2..49c34de7aa 100644
--- a/core/modules/update/tests/modules/update_test/drupal.0.1-alpha1.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.0.1-alpha1.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.0.1-beta1.xml b/core/modules/update/tests/modules/update_test/drupal.0.1-beta1.xml
index 55f4f32cbb..46c1a7e5ab 100644
--- a/core/modules/update/tests/modules/update_test/drupal.0.1-beta1.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.0.1-beta1.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.0.1.xml b/core/modules/update/tests/modules/update_test/drupal.0.1.xml
index 8ae882cdb4..7231ff0649 100644
--- a/core/modules/update/tests/modules/update_test/drupal.0.1.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.0.1.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.1.0-alpha1.xml b/core/modules/update/tests/modules/update_test/drupal.1.0-alpha1.xml
index 74de5411f2..4125caed95 100644
--- a/core/modules/update/tests/modules/update_test/drupal.1.0-alpha1.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.1.0-alpha1.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.1.0-beta1.xml b/core/modules/update/tests/modules/update_test/drupal.1.0-beta1.xml
index 8f0177d903..c46b9453f8 100644
--- a/core/modules/update/tests/modules/update_test/drupal.1.0-beta1.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.1.0-beta1.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.1.0.xml b/core/modules/update/tests/modules/update_test/drupal.1.0.xml
index c76319d57c..f2424638d3 100644
--- a/core/modules/update/tests/modules/update_test/drupal.1.0.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.1.0.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.1.1-alpha1.xml b/core/modules/update/tests/modules/update_test/drupal.1.1-alpha1.xml
index c0952c905d..3abb7fab44 100644
--- a/core/modules/update/tests/modules/update_test/drupal.1.1-alpha1.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.1.1-alpha1.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.1.1-beta1.xml b/core/modules/update/tests/modules/update_test/drupal.1.1-beta1.xml
index e3a3264b7e..50ae5c77c2 100644
--- a/core/modules/update/tests/modules/update_test/drupal.1.1-beta1.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.1.1-beta1.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.1.1.xml b/core/modules/update/tests/modules/update_test/drupal.1.1.xml
index af0fb6ae78..22fb150713 100644
--- a/core/modules/update/tests/modules/update_test/drupal.1.1.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.1.1.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.9.xml b/core/modules/update/tests/modules/update_test/drupal.9.xml
index 6b62d122a9..b3f4bd0371 100644
--- a/core/modules/update/tests/modules/update_test/drupal.9.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.9.xml
@@ -6,7 +6,6 @@
 <api_version>9.x</api_version>
 <recommended_branch>9.0.</recommended_branch>
 <supported_branches>9.0.</supported_branches>
-<default_major>9</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.dev.xml b/core/modules/update/tests/modules/update_test/drupal.dev.xml
index c53fd11289..b95d34c316 100644
--- a/core/modules/update/tests/modules/update_test/drupal.dev.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.dev.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.sec.0.1_0.2.xml b/core/modules/update/tests/modules/update_test/drupal.sec.0.1_0.2.xml
index 216c236ed3..7aeb360c98 100644
--- a/core/modules/update/tests/modules/update_test/drupal.sec.0.1_0.2.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.sec.0.1_0.2.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.sec.0.2-rc2-b.xml b/core/modules/update/tests/modules/update_test/drupal.sec.0.2-rc2-b.xml
index 76eed9b1c5..ac3785faef 100644
--- a/core/modules/update/tests/modules/update_test/drupal.sec.0.2-rc2-b.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.sec.0.2-rc2-b.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.,8.2.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.sec.0.2-rc2.xml b/core/modules/update/tests/modules/update_test/drupal.sec.0.2-rc2.xml
index 06e6674323..af63215dfb 100644
--- a/core/modules/update/tests/modules/update_test/drupal.sec.0.2-rc2.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.sec.0.2-rc2.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.,8.2.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.sec.0.2.xml b/core/modules/update/tests/modules/update_test/drupal.sec.0.2.xml
index 46dd668793..6a6141eb8b 100644
--- a/core/modules/update/tests/modules/update_test/drupal.sec.0.2.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.sec.0.2.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.sec.1.2.xml b/core/modules/update/tests/modules/update_test/drupal.sec.1.2.xml
index ae2a2b07a4..7f636e9622 100644
--- a/core/modules/update/tests/modules/update_test/drupal.sec.1.2.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.sec.1.2.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/drupal.sec.1.2_insecure.xml b/core/modules/update/tests/modules/update_test/drupal.sec.1.2_insecure.xml
index d1cb15f376..f45c980180 100644
--- a/core/modules/update/tests/modules/update_test/drupal.sec.1.2_insecure.xml
+++ b/core/modules/update/tests/modules/update_test/drupal.sec.1.2_insecure.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.0.</recommended_branch>
 <supported_branches>8.0.,8.1.</supported_branches>
-<default_major>8</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/drupal</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/update_test_basetheme.1_1-sec.xml b/core/modules/update/tests/modules/update_test/update_test_basetheme.1_1-sec.xml
index 43ea623454..be8e02aa6f 100644
--- a/core/modules/update/tests/modules/update_test/update_test_basetheme.1_1-sec.xml
+++ b/core/modules/update/tests/modules/update_test/update_test_basetheme.1_1-sec.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.x-1.</recommended_branch>
 <supported_branches>8.x-1.</supported_branches>
-<default_major>1</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/update_test_basetheme</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/update_test_new_module.1_1.xml b/core/modules/update/tests/modules/update_test/update_test_new_module.1_1.xml
index 58f8247168..8f07f12e54 100644
--- a/core/modules/update/tests/modules/update_test/update_test_new_module.1_1.xml
+++ b/core/modules/update/tests/modules/update_test/update_test_new_module.1_1.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.x-1.</recommended_branch>
 <supported_branches>8.x-1.</supported_branches>
-<default_major>1</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/update_test_new_module</link>
   <terms>
diff --git a/core/modules/update/tests/modules/update_test/update_test_subtheme.1_0.xml b/core/modules/update/tests/modules/update_test/update_test_subtheme.1_0.xml
index 2b1ddbf0aa..3b1932b537 100644
--- a/core/modules/update/tests/modules/update_test/update_test_subtheme.1_0.xml
+++ b/core/modules/update/tests/modules/update_test/update_test_subtheme.1_0.xml
@@ -6,7 +6,6 @@
 <api_version>8.x</api_version>
 <recommended_branch>8.x-1.</recommended_branch>
 <supported_branches>8.x-1.</supported_branches>
-<default_major>1</default_major>
 <project_status>published</project_status>
 <link>http://example.com/project/update_test_subtheme</link>
   <terms>
diff --git a/core/modules/update/update.compare.inc b/core/modules/update/update.compare.inc
index be79cce0af..4ed6957c1c 100644
--- a/core/modules/update/update.compare.inc
+++ b/core/modules/update/update.compare.inc
@@ -241,25 +241,18 @@ function update_calculate_project_update_status(&$project_data, $available) {
     $supported_branches = explode(',', $available['supported_branches']);
   }
 
-
   if (in_array($existing_version_parser->getSupportBranch(), $supported_branches)) {
     // Still supported, stay at the current major version.
     $target_major = $existing_major;
   }
   elseif (isset($available['recommended_branch'])) {
-    // Since 'recommended_branch' is defined, we know this is the new XML
-    // format. Therefore, we know the current release is unsupported since
+    // We know the current release is unsupported since
     // its major version was not in the 'supported_branches' list. We should
     // find the best release from the recommended major version.
     $branch_version_parser = new ModuleVersionParser($available['recommended_branch'] . 'x');
     $target_major = $branch_version_parser->getMajorVersion();
     $project_data['status'] = UPDATE_NOT_SUPPORTED;
   }
-  elseif (isset($available['default_major'])) {
-    // Older release history XML file without recommended, so recommend
-    // the currently defined "default_major" version.
-    $target_major = $available['default_major'];
-  }
   else {
     // Malformed XML file? Stick with the current branch.
     $target_major = $existing_major;