.../big_pipe_regression_test.routing.yml           |  7 ++++++
 .../src/BigPipeRegressionTestController.php        | 26 ++++++++++++++++++++++
 .../FunctionalJavascript/BigPipeRegressionTest.php | 12 ++++++++++
 3 files changed, 45 insertions(+)

diff --git a/core/modules/big_pipe/tests/modules/big_pipe_regression_test/big_pipe_regression_test.routing.yml b/core/modules/big_pipe/tests/modules/big_pipe_regression_test/big_pipe_regression_test.routing.yml
index a2fc417..bd0543b 100644
--- a/core/modules/big_pipe/tests/modules/big_pipe_regression_test/big_pipe_regression_test.routing.yml
+++ b/core/modules/big_pipe/tests/modules/big_pipe_regression_test/big_pipe_regression_test.routing.yml
@@ -4,3 +4,10 @@ big_pipe_regression_test.2678662:
     _controller: '\Drupal\big_pipe_regression_test\BigPipeRegressionTestController::regression2678662'
   requirements:
     _access: 'TRUE'
+
+big_pipe_regression_test.2802923:
+  path: '/big_pipe_regression_test/2802923'
+  defaults:
+    _controller: '\Drupal\big_pipe_regression_test\BigPipeRegressionTestController::regression2802923'
+  requirements:
+    _access: 'TRUE'
diff --git a/core/modules/big_pipe/tests/modules/big_pipe_regression_test/src/BigPipeRegressionTestController.php b/core/modules/big_pipe/tests/modules/big_pipe_regression_test/src/BigPipeRegressionTestController.php
index f42c89c..50e618b 100644
--- a/core/modules/big_pipe/tests/modules/big_pipe_regression_test/src/BigPipeRegressionTestController.php
+++ b/core/modules/big_pipe/tests/modules/big_pipe_regression_test/src/BigPipeRegressionTestController.php
@@ -17,4 +17,30 @@ public function regression2678662() {
     ];
   }
 
+  /**
+   * @see \Drupal\Tests\big_pipe\FunctionalJavascript\BigPipeRegressionTest::testMultipleBodies_2678662()
+   */
+  public function regression2802923() {
+    return [
+      '#prefix' => BigPipeMarkup::create('<p>Hi, my train will arrive at '),
+      'time' => [
+        '#lazy_builder' => [static::class . '::currentTime', []],
+        '#create_placeholder' => TRUE,
+      ],
+      '#suffix' => BigPipeMarkup::create(' — will I still be able to catch the connection to the center?</p>'),
+    ];
+  }
+
+  /**
+   * #lazy_builder callback; builds <time> markup with current time.
+   *
+   * @return array
+   */
+  public static function currentTime() {
+    return [
+      '#markup' => '<time datetime="' . date('Y-m-d', time()) . '"></time>',
+      '#cache' => ['max-age' => 0]
+    ];
+  }
+
 }
diff --git a/core/modules/big_pipe/tests/src/FunctionalJavascript/BigPipeRegressionTest.php b/core/modules/big_pipe/tests/src/FunctionalJavascript/BigPipeRegressionTest.php
index a99d5fc..b4da7b0 100644
--- a/core/modules/big_pipe/tests/src/FunctionalJavascript/BigPipeRegressionTest.php
+++ b/core/modules/big_pipe/tests/src/FunctionalJavascript/BigPipeRegressionTest.php
@@ -184,4 +184,16 @@ public function testMessages_2712935() {
     }
   }
 
+  /**
+   * Ensure default BigPipe placeholder HTML cannot split paragraphs.
+   *
+   * @see https://www.drupal.org/node/2802923
+   */
+  public function testPlaceholderInParagraph_2802923() {
+    $this->drupalLogin($this->drupalCreateUser());
+    $this->drupalGet(Url::fromRoute('big_pipe_regression_test.2802923'));
+
+    $this->assertJsCondition('document.querySelectorAll(\'p\').length === 1');
+  }
+
 }