core/modules/big_pipe/src/Render/BigPipe.php    |  4 ++++
 core/modules/big_pipe/src/Tests/BigPipeTest.php | 13 ++++++++++++-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/core/modules/big_pipe/src/Render/BigPipe.php b/core/modules/big_pipe/src/Render/BigPipe.php
index 003822a..967a8ce 100644
--- a/core/modules/big_pipe/src/Render/BigPipe.php
+++ b/core/modules/big_pipe/src/Render/BigPipe.php
@@ -252,6 +252,7 @@ protected function sendNoJsPlaceholders($html, $no_js_placeholders, AttachedAsse
           throw $e;
         }
         else {
+          trigger_error($e, E_USER_ERROR);
           continue;
         }
       }
@@ -288,6 +289,7 @@ protected function sendNoJsPlaceholders($html, $no_js_placeholders, AttachedAsse
           throw $e;
         }
         else {
+          trigger_error($e, E_USER_ERROR);
           continue;
         }
       }
@@ -362,6 +364,7 @@ protected function sendPlaceholders(array $placeholders, array $placeholder_orde
           throw $e;
         }
         else {
+          trigger_error($e, E_USER_ERROR);
           continue;
         }
       }
@@ -394,6 +397,7 @@ protected function sendPlaceholders(array $placeholders, array $placeholder_orde
           throw $e;
         }
         else {
+          trigger_error($e, E_USER_ERROR);
           continue;
         }
       }
diff --git a/core/modules/big_pipe/src/Tests/BigPipeTest.php b/core/modules/big_pipe/src/Tests/BigPipeTest.php
index 1b43663..26025a5 100644
--- a/core/modules/big_pipe/src/Tests/BigPipeTest.php
+++ b/core/modules/big_pipe/src/Tests/BigPipeTest.php
@@ -11,6 +11,7 @@
 use Drupal\big_pipe\Render\BigPipe;
 use Drupal\Component\Serialization\Json;
 use Drupal\Component\Utility\Html;
+use Drupal\Core\Logger\RfcLogLevel;
 use Drupal\Core\Url;
 use Drupal\simpletest\WebTestBase;
 
@@ -32,7 +33,7 @@ class BigPipeTest extends WebTestBase {
    *
    * @var array
    */
-  public static $modules = ['big_pipe', 'big_pipe_test'];
+  public static $modules = ['big_pipe', 'big_pipe_test', 'dblog'];
 
   /**
    * {@inheritdoc}
@@ -152,6 +153,8 @@ public function testBigPipe() {
     $this->assertSessionCookieExists(TRUE);
     $this->assertBigPipeNoJsCookieExists(FALSE);
 
+    $log_count = db_query('SELECT COUNT(*) FROM {watchdog}')->fetchField();
+
     // By not calling performMetaRefresh() here, we simulate JavaScript being
     // enabled, because as far as the BigPipe module is concerned, JavaScript is
     // enabled in the browser as long as the BigPipe no-JS cookie is *not* set.
@@ -180,6 +183,14 @@ public function testBigPipe() {
     $this->assertFalse(empty($this->getDrupalSettings()), 'drupalSettings present.');
     $this->assertTrue(in_array('big_pipe/big_pipe', explode(',', $this->getDrupalSettings()['ajaxPageState']['libraries'])), 'BigPipe asset library is present.');
 
+    // Verify that the two expected exceptions are logged as errors.
+    $this->assertEqual($log_count + 2, db_query('SELECT COUNT(*) FROM {watchdog}')->fetchField(), 'Two new watchdog entries.');
+    $records = db_query('SELECT * FROM {watchdog} ORDER BY wid DESC LIMIT 2')->fetchAll();
+    $this->assertEqual(RfcLogLevel::ERROR, $records[0]->severity);
+    $this->assertTrue(FALSE !== strpos((string) unserialize($records[0]->variables)['@message'], "exception 'Exception' with message 'Oh noes!'"));
+    $this->assertEqual(RfcLogLevel::ERROR, $records[0]->severity);
+    $this->assertTrue(FALSE !== strpos((string) unserialize($records[1]->variables)['@message'], "exception 'Exception' with message 'You are not allowed to say llamas are not cool!'"));
+
     // Verify that 4xx responses work fine. (4xx responses are handled by
     // subrequests to a route pointing to a controller with the desired output.)
     $this->drupalGet(Url::fromUri('base:non-existing-path'));