diff --git a/src/Utility/FieldsHelper.php b/src/Utility/FieldsHelper.php
index c9ddc4c3..3caa4d86 100644
--- a/src/Utility/FieldsHelper.php
+++ b/src/Utility/FieldsHelper.php
@@ -257,9 +257,13 @@ public function extractItemValues(array $items, array $required_properties, $loa
           // already been processed in some way, or use a data type that
           // transformed their original value. But that will hopefully not be a
           // problem in most situations.
-          foreach ($this->filterForPropertyPath($item->getFields(FALSE), $datasource_id, $property_path) as $field) {
+          // In case of duplicates (for configurable fields, mostly) we prefer
+          // the one matching the given $combined_id, since several callers (for
+          // instance, the Highlight processor) pass the field ID there.
+          $field = $this->findField($item->getFields(FALSE), $datasource_id, $property_path, $combined_id);
+          if ($field) {
             $item_values[$combined_id] = $field->getValues();
-            continue 2;
+            continue;
           }
 
           // There are no values present on the item for this property. If we
@@ -288,9 +292,9 @@ public function extractItemValues(array $items, array $required_properties, $loa
               // If the index contains a field with that property, just use the
               // configuration from there instead of the default configuration.
               // This will probably be what users expect in most situations.
-              foreach ($this->filterForPropertyPath($index->getFields(), $datasource_id, $property_path) as $field) {
+              $field = $this->findField($index->getFields(), $datasource_id, $property_path, $combined_id);
+              if ($field) {
                 $field_info['configuration'] = $field->getConfiguration();
-                break;
               }
             }
             $processor_fields[] = $this->createField($index, $combined_id, $field_info);
@@ -330,6 +334,36 @@ public function extractItemValues(array $items, array $required_properties, $loa
     return $extracted_values;
   }
 
+  /**
+   * Finds a field within an array of fields.
+   *
+   * @param \Drupal\search_api\Item\FieldInterface[] $fields
+   *   The fields to search.
+   * @param string|null $datasource_id
+   *   The datasource ID of the field that should be found.
+   * @param string $property_path
+   *   The property path of the field that should be found.
+   * @param string|null $preferred_field_id
+   *   (optional) The preferred field ID: if multiple fields are found matching
+   *   the given datasource and property path, but one has this field ID, then
+   *   that field is returned. Otherwise, the returned field is undefined.
+   *
+   * @return \Drupal\search_api\Item\FieldInterface|null
+   *   The found field, or NULL if it couldn't be found.
+   */
+  protected function findField(array $fields, ?string $datasource_id, string $property_path, ?string $preferred_field_id = NULL): ?FieldInterface {
+    $return = NULL;
+    foreach ($this->filterForPropertyPath($fields, $datasource_id, $property_path) as $field) {
+      if ($field->getFieldIdentifier() === $preferred_field_id) {
+        return $field;
+      }
+      elseif (!$return) {
+        $return = $field;
+      }
+    }
+    return $return;
+  }
+
   /**
    * {@inheritdoc}
    */
diff --git a/tests/src/Kernel/Processor/HighlightExcerptTest.php b/tests/src/Kernel/Processor/HighlightExcerptTest.php
new file mode 100644
index 00000000..d2d2ef1e
--- /dev/null
+++ b/tests/src/Kernel/Processor/HighlightExcerptTest.php
@@ -0,0 +1,196 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Drupal\Tests\search_api\Kernel\Processor;
+
+use Drupal\comment\Entity\Comment;
+use Drupal\comment\Tests\CommentTestTrait;
+use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\node\Entity\Node;
+use Drupal\node\Entity\NodeType;
+use Drupal\search_api\Item\Field;
+use Drupal\search_api\Processor\ProcessorInterface;
+use Drupal\search_api\Query\ResultSetInterface;
+use Drupal\search_api\Utility\Utility;
+use Drupal\Tests\node\Traits\ContentTypeCreationTrait;
+
+/**
+ * Tests generation of highlighted excerpts by the "Highlight" processor.
+ *
+ * @see \Drupal\search_api\Plugin\search_api\processor\Highlight
+ */
+class HighlightExcerptTest extends ProcessorTestBase {
+
+  use CommentTestTrait;
+  use ContentTypeCreationTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'filter',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp($processor = NULL): void {
+    parent::setUp('highlight');
+
+    FieldStorageConfig::create([
+      'type' => 'text_long',
+      'entity_type' => 'node',
+      'field_name' => 'body',
+    ])->save();
+    $this->createContentType(['type' => 'article']);
+    FieldStorageConfig::create([
+      'type' => 'text_long',
+      'entity_type' => 'comment',
+      'field_name' => 'comment_body',
+    ])->save();
+    $this->addDefaultCommentField('node', 'article');
+  }
+
+  /**
+   * Tests the generation of excerpts from multiple aggregated fields.
+   */
+  public function testExcerptGenerationMultipleAggregatedFields(): void {
+    // Set up two aggregated fields, one date field that shouldn't matter and
+    // one field containing the fulltext contents.
+    $changed_field = (new Field($this->index, 'changed'))
+      ->setType('date')
+      ->setPropertyPath('aggregated_field')
+      ->setLabel('Changed')
+      ->setConfiguration([
+        'type' => 'union',
+        'fields' => [
+          Utility::createCombinedId('entity:comment', 'changed'),
+          Utility::createCombinedId('entity:node', 'changed'),
+        ],
+      ]);
+    $this->index->addField($changed_field);
+
+    $body_field = (new Field($this->index, 'content'))
+      ->setType('text')
+      ->setPropertyPath('aggregated_field')
+      ->setLabel('Body')
+      ->setConfiguration([
+        'type' => 'union',
+        'fields' => [
+          Utility::createCombinedId('entity:comment', 'comment_body'),
+          Utility::createCombinedId('entity:node', 'body'),
+        ],
+      ]);
+    $this->index->addField($body_field);
+
+    $this->index->save();
+
+    // Create a node and comment, both of which should contain the word "test"
+    // in the "content" aggregated field (but not anywhere else).
+    $node = Node::create([
+      'type' => 'article',
+      'title' => 'Foo',
+      'body' => 'This is a test for the excerpt.',
+      'uid' => 0,
+    ]);
+    $node->save();
+    $comment = Comment::create([
+      'entity_type' => 'node',
+      'entity_id' => $node->id(),
+      'name' => 'Carla',
+      'mail' => 'foo@example.com',
+      'comment_body' => 'Comment on the test node.',
+      'comment_type' => 'comment',
+      'field_name' => 'comment',
+      'pid' => 0,
+      'uid' => 0,
+      'status' => 1,
+    ]);
+    $comment->save();
+
+    $this->indexItems();
+
+    // Now search for "test" and verify that the excerpt is not empty and
+    // contains the highlighted keyword as expected.
+    $results = $this->index->query()
+      ->keys('test')
+      ->execute();
+    $this->assertEquals(2, $results->getResultCount());
+    $items = $results->getResultItems();
+    $this->assertCount(2, $items);
+    $node_item_id = "entity:node/{$node->id()}:en";
+    $this->assertArrayHasKey($node_item_id, $items);
+    $comment_item_id = "entity:comment/{$comment->id()}:en";
+    $this->assertArrayHasKey($comment_item_id, $items);
+
+    $node_result = $items[$node_item_id];
+    $excerpt = $node_result->getExcerpt();
+    $this->assertNotEmpty($excerpt);
+    $this->assertStringContainsString('<strong>test</strong>', $excerpt);
+
+    $comment_result = $items[$comment_item_id];
+    $excerpt = $comment_result->getExcerpt();
+    $this->assertNotEmpty($excerpt);
+    $this->assertStringContainsString('<strong>test</strong>', $excerpt);
+
+    // Simulate a backend that includes the field values in the search results
+    // and verify that this works correctly in that scenario, too.
+    $processor = $this->createMock(ProcessorInterface::class);
+    $processor->method('getPluginId')->willReturn('test');
+    $processor->method('supportsStage')
+        ->willReturnCallback(function (string $stage): bool {
+        return $stage === ProcessorInterface::STAGE_POSTPROCESS_QUERY;
+      });
+    $processor->method('getWeight')->willReturn(-50);
+    $processor->method('postprocessSearchResults')
+      ->willReturnCallback(function (ResultSetInterface $results) use ($node_item_id, $comment_item_id): void {
+        foreach ($results->getResultItems() as $item_id => $item) {
+          // Add a flag so we can make sure this processor ran.
+          $item->setExtraData(static::class, TRUE);
+
+          $changed_field = clone $this->index->getField('changed');
+          $item->setField('changed', $changed_field);
+          $content_field = clone $this->index->getField('content');
+          $item->setField('content', $content_field);
+          switch ($item_id) {
+            case $node_item_id:
+              $changed_field->addValue(1234567890);
+              $content_field->addValue('This is a test for the excerpt.');
+              break;
+            case $comment_item_id:
+              $changed_field->addValue(1234567890);
+              $content_field->addValue('Comment on the test node.');
+              break;
+
+            default:
+              assert(FALSE, "Unexpected item ID \"$item_id\".");
+          }
+        }
+      });
+    $this->index->addProcessor($processor);
+
+    // Repeat the search and checks, as above.
+    $results = $this->index->query()
+      ->keys('test')
+      ->execute();
+    $this->assertEquals(2, $results->getResultCount());
+    $items = $results->getResultItems();
+    $this->assertCount(2, $items);
+    $this->assertArrayHasKey($node_item_id, $items);
+    $this->assertArrayHasKey($comment_item_id, $items);
+
+    $node_result = $items[$node_item_id];
+    $this->assertNotEmpty($node_result->getExtraData(static::class));
+    $excerpt = $node_result->getExcerpt();
+    $this->assertNotEmpty($excerpt);
+    $this->assertStringContainsString('<strong>test</strong>', $excerpt);
+
+    $comment_result = $items[$comment_item_id];
+    $this->assertNotEmpty($comment_result->getExtraData(static::class));
+    $excerpt = $comment_result->getExcerpt();
+    $this->assertNotEmpty($excerpt);
+    $this->assertStringContainsString('<strong>test</strong>', $excerpt);
+  }
+
+}