diff --git a/core/lib/Drupal/Component/Serialization/YamlSymfony.php b/core/lib/Drupal/Component/Serialization/YamlSymfony.php
index d35e09c..1cbebff 100644
--- a/core/lib/Drupal/Component/Serialization/YamlSymfony.php
+++ b/core/lib/Drupal/Component/Serialization/YamlSymfony.php
@@ -30,13 +30,34 @@ public static function encode($data) {
    * {@inheritdoc}
    */
   public static function decode($raw) {
+    // Workaround for PHP 7 bug #70110 that causes the symfony yaml parser to
+    // fail on some strings, for example those containing a lot of newlines.
+    // @see https://bugs.php.net/bug.php?id=70110
+    // @see https://www.drupal.org/node/2792877
+    $reactivate_pcre_jit = 0;
+    if (version_compare(phpversion(), '7', '>=')) {
+      if ($reactivate_pcre_jit = ini_get('pcre.jit')) {
+        // Turn off jit while parsing YAML files.
+        ini_set('pcre.jit', 0);
+      }
+    }
+
     try {
       $yaml = new Parser();
       // Make sure we have a single trailing newline. A very simple config like
       // 'foo: bar' with no newline will fail to parse otherwise.
-      return $yaml->parse($raw, SymfonyYaml::PARSE_EXCEPTION_ON_INVALID_TYPE);
+      $parsed = $yaml->parse($raw, SymfonyYaml::PARSE_EXCEPTION_ON_INVALID_TYPE);
+      if ($reactivate_pcre_jit) {
+        // Turn back on jit for performance.
+        ini_set('pcre.jit', 1);
+      }
+      return $parsed;
     }
     catch (\Exception $e) {
+      if ($reactivate_pcre_jit) {
+        // Turn back on jit for performance.
+        ini_set('pcre.jit', 1);
+      }
       throw new InvalidDataTypeException($e->getMessage(), $e->getCode(), $e);
     }
   }
diff --git a/core/tests/Drupal/Tests/Component/Serialization/YamlSymfonyTest.php b/core/tests/Drupal/Tests/Component/Serialization/YamlSymfonyTest.php
index 86c818c..89ac70d 100644
--- a/core/tests/Drupal/Tests/Component/Serialization/YamlSymfonyTest.php
+++ b/core/tests/Drupal/Tests/Component/Serialization/YamlSymfonyTest.php
@@ -75,4 +75,20 @@ public function testObjectSupportDisabled() {
     YamlSymfony::encode([$object]);
   }
 
+  /**
+   * Tests that preg jit compiler doesn't break decoding strings with newlines.
+   *
+   * @covers ::decode
+   */
+  public function testNewlines() {
+    $string = str_repeat('\n', 2700);
+    $yaml = 'string: "' . $string . '"';
+    $config = YamlSymfony::decode($yaml);
+    $this->assertEquals(str_repeat("\n", 2700), $config['string']);
+
+    $string = str_repeat('\n', 2800);
+    $yaml = 'string: "' . $string . '"';
+    $config = YamlSymfony::decode($yaml);
+    $this->assertEquals(str_repeat("\n", 2800), $config['string']);
+  }
 }