diff --git a/CHANGELOG b/CHANGELOG
index cbe48fa0c7..1f5a4cbe38 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,6 @@
 * 1.42.1 (2019-XX-XX)
 
+ * added support for "Twig\Markup" instances in the "in" test (again)
  * allowed string operators as variables names in assignments
 
 * 1.42.0 (2019-05-31)
diff --git a/src/Extension/CoreExtension.php b/src/Extension/CoreExtension.php
index 2e564ebe78..80ced9815c 100644
--- a/src/Extension/CoreExtension.php
+++ b/src/Extension/CoreExtension.php
@@ -943,6 +943,9 @@ function twig_in_filter($value, $compare)
     if ($value instanceof Markup) {
         $value = (string) $value;
     }
+    if ($compare instanceof Markup) {
+        $compare = (string) $compare;
+    }
 
     if (\is_array($compare)) {
         return \in_array($value, $compare, \is_object($value) || \is_resource($value));
diff --git a/test/Twig/Tests/Fixtures/tests/in.test b/test/Twig/Tests/Fixtures/tests/in.test
index e3ebf05590..f7b172e8d0 100644
--- a/test/Twig/Tests/Fixtures/tests/in.test
+++ b/test/Twig/Tests/Fixtures/tests/in.test
@@ -56,6 +56,7 @@ Twig supports the in operator
 {{ '5.5' in 125.5 ? 'KO' : 'OK' }}
 
 {{ safe in ['foo', 'bar'] ? 'OK' : 'KO' }}
+{{ 'fo' in safe ? 'OK' : 'KO' }}
 --DATA--
 return ['bar' => 'bar', 'foo' => ['bar' => 'bar'], 'dir_object' => new \SplFileInfo(dirname(__FILE__)), 'object' => new \stdClass(), 'resource' => opendir(dirname(__FILE__)), 'safe' => new \Twig\Markup('foo', 'UTF-8')]
 --EXPECT--
@@ -114,3 +115,4 @@ OK
 OK
 
 OK
+OK