diff --git a/core/modules/content_translation/src/FieldTranslationSynchronizer.php b/core/modules/content_translation/src/FieldTranslationSynchronizer.php
index e900c5086c..3f3595ecbd 100644
--- a/core/modules/content_translation/src/FieldTranslationSynchronizer.php
+++ b/core/modules/content_translation/src/FieldTranslationSynchronizer.php
@@ -92,18 +92,38 @@ public function synchronizeFields(ContentEntityInterface $entity, $sync_langcode
       return;
     }
 
-    if ($entity->isDefaultTranslationAffectedOnly()) {
-      // If changes to untranslatable fields are configured to affect only the
-      // default translation, we need to skip synchronization in pending
-      // revisions, otherwise multiple translations would be affected.
-      if (!$entity->isDefaultRevision()) {
-        return;
+    if ($entity->isNewRevision()) {
+      if ($entity->isDefaultTranslationAffectedOnly()) {
+        // If changes to untranslatable fields are configured to affect only the
+        // default translation, we need to skip synchronization in pending
+        // revisions, otherwise multiple translations would be affected.
+        if (!$entity->isDefaultRevision()) {
+          return;
+        }
+        // When this mode is enabled, changes to synchronized properties are
+        // allowed only in the default translation, thus we need to make sure this
+        // is always used as source for the synchronization process.
+        else {
+          $sync_langcode = $entity->getUntranslated()->language()->getId();
+        }
       }
-      // When this mode is enabled, changes to synchronized properties are
-      // allowed only in the default translation, thus we need to make sure this
-      // is always used as source for the synchronization process.
-      else {
-        $sync_langcode = $entity->getUntranslated()->language()->getId();
+      elseif ($entity->isDefaultRevision()) {
+        // If a new default revision is being saved, but a newer default
+        // revision was created meanwhile, use any other translation as source
+        // for synchronization, since that will have been merged from the
+        // default revision. In this case the actual language does not matter as
+        // synchronized properties are the same for all the translations in the
+        // default revision.
+        /** @var \Drupal\Core\Entity\ContentEntityInterface $default_revision */
+        $default_revision = $this->entityManager
+          ->getStorage($entity->getEntityTypeId())
+          ->load($entity->id());
+        if ($default_revision->getLoadedRevisionId() !== $entity->getLoadedRevisionId()) {
+          $other_langcodes = array_diff_key($default_revision->getTranslationLanguages(), [$sync_langcode => FALSE]);
+          if ($other_langcodes) {
+            $sync_langcode = key($other_langcodes);
+          }
+        }
       }
     }
 
diff --git a/core/modules/content_translation/tests/src/Kernel/ContentTranslationFieldSyncValidationTest.php b/core/modules/content_translation/tests/src/Kernel/ContentTranslationFieldSyncRevisionTest.php
similarity index 86%
rename from core/modules/content_translation/tests/src/Kernel/ContentTranslationFieldSyncValidationTest.php
rename to core/modules/content_translation/tests/src/Kernel/ContentTranslationFieldSyncRevisionTest.php
index 4c75e62785..c1d1e272fb 100644
--- a/core/modules/content_translation/tests/src/Kernel/ContentTranslationFieldSyncValidationTest.php
+++ b/core/modules/content_translation/tests/src/Kernel/ContentTranslationFieldSyncRevisionTest.php
@@ -15,13 +15,11 @@
 use Drupal\user\Entity\User;
 
 /**
- * Tests the field synchronization validation logic.
+ * Tests the field synchronization logic when revisions are involved.
  *
  * @group content_translation
- *
- * @coversDefaultClass \Drupal\content_translation\Plugin\Validation\Constraint\ContentTranslationSynchronizedFieldsConstraintValidator
  */
-class ContentTranslationFieldSyncValidationTest extends EntityKernelTestBase {
+class ContentTranslationFieldSyncRevisionTest extends EntityKernelTestBase {
 
   use TestFileCreationTrait;
 
@@ -114,14 +112,16 @@ protected function setUp() {
   }
 
   /**
-   * Checks that pending revision validation works as expected.
+   * Checks that field synchronization works as expected with revisions.
    *
-   * @covers ::__construct
-   * @covers ::create
-   * @covers ::validate
-   * @covers ::hasSynchronizedPropertyChanges
+   * @covers \Drupal\content_translation\Plugin\Validation\Constraint\ContentTranslationSynchronizedFieldsConstraintValidator::create
+   * @covers \Drupal\content_translation\Plugin\Validation\Constraint\ContentTranslationSynchronizedFieldsConstraintValidator::validate
+   * @covers \Drupal\content_translation\Plugin\Validation\Constraint\ContentTranslationSynchronizedFieldsConstraintValidator::hasSynchronizedPropertyChanges
+   * @covers \Drupal\content_translation\FieldTranslationSynchronizer::getFieldSynchronizedProperties
+   * @covers \Drupal\content_translation\FieldTranslationSynchronizer::synchronizeFields
+   * @covers \Drupal\content_translation\FieldTranslationSynchronizer::synchronizeItems
    */
-  public function testPendingRevisionValidation() {
+  public function testFieldSynchronizationAndValidation() {
     // Test that when untranslatable field widgets are displayed, synchronized
     // field properties can be changed only in default revisions.
     $this->setUntranslatableFieldWidgetsDisplay(TRUE);
@@ -332,6 +332,41 @@ public function testPendingRevisionValidation() {
     $en_revision->getTranslation('it')->get($this->fieldName)->alt = 'Alt 3 IT';
     $violations = $en_revision->validate();
     $this->assertViolations($violations);
+
+    // Test that when saving a new default revision starting from a pending
+    // revision, outdated synchronized properties do not override more recent
+    // ones.
+    $this->setUntranslatableFieldWidgetsDisplay(TRUE);
+    $entity = $this->saveNewEntity();
+    $entity_id = $entity->id();
+    $this->assertLatestRevisionFieldValues($entity_id, [23, 1, 1, 'Alt 1 EN']);
+
+    $it_translation = $entity->addTranslation('it', $entity->toArray());
+    /** @var \Drupal\Core\Entity\ContentEntityInterface $it_revision */
+    $it_revision = $this->createRevision($it_translation, FALSE);
+    $metadata = $this->contentTranslationManager->getTranslationMetadata($it_revision);
+    $metadata->setSource('en');
+    $it_revision->get($this->fieldName)->alt = 'Alt 2 IT';
+    $violations = $it_revision->validate();
+    $this->assertEmpty($violations);
+    $this->storage->save($it_revision);
+    $this->assertLatestRevisionFieldValues($entity_id, [24, 1, 1, 'Alt 1 EN', 'Alt 2 IT']);
+
+    /** @var \Drupal\Core\Entity\ContentEntityInterface $en_revision */
+    $en_revision = $this->createRevision($entity);
+    $en_revision->get($this->fieldName)->target_id = 3;
+    $en_revision->get($this->fieldName)->alt = 'Alt 3 EN';
+    $violations = $en_revision->validate();
+    $this->assertEmpty($violations);
+    $this->storage->save($en_revision);
+    $this->assertLatestRevisionFieldValues($entity_id, [25, 3, 3, 'Alt 3 EN', 'Alt 2 IT']);
+
+    $it_revision = $this->createRevision($it_revision);
+    $it_revision->get($this->fieldName)->alt = 'Alt 4 IT';
+    $violations = $it_revision->validate();
+    $this->assertEmpty($violations);
+    $this->storage->save($it_revision);
+    $this->assertLatestRevisionFieldValues($entity_id, [26, 3, 3, 'Alt 3 EN', 'Alt 4 IT']);
   }
 
   /**