diff --git a/CHANGELOG b/CHANGELOG
index 7798f3372..61b1c32be 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,6 @@
 * 1.38.4 (2019-XX-XX)
 
- * n/a
+ * fixed CheckToStringNode implementation (broken when a function/filter is variadic)
 
 * 1.38.3 (2019-03-21)
 
diff --git a/src/Node/CheckToStringNode.php b/src/Node/CheckToStringNode.php
index 464c96fba..5d6746791 100644
--- a/src/Node/CheckToStringNode.php
+++ b/src/Node/CheckToStringNode.php
@@ -24,7 +24,7 @@ use Twig\Node\Expression\AbstractExpression;
  *
  * @author Fabien Potencier <fabien@symfony.com>
  */
-class CheckToStringNode extends Node
+class CheckToStringNode extends AbstractExpression
 {
     public function __construct(AbstractExpression $expr)
     {
diff --git a/test/Twig/Tests/Fixtures/tags/sandbox/array.test b/test/Twig/Tests/Fixtures/tags/sandbox/array.test
new file mode 100644
index 000000000..b432427e4
--- /dev/null
+++ b/test/Twig/Tests/Fixtures/tags/sandbox/array.test
@@ -0,0 +1,16 @@
+--TEST--
+sandbox tag
+--TEMPLATE--
+{%- sandbox %}
+    {%- include "foo.twig" %}
+{%- endsandbox %}
+--TEMPLATE(foo.twig)--
+{{ [a][0] }}
+{{ dump([a][0]) }}
+--DATA--
+return ['a' => 'b']
+--CONFIG--
+return ['autoescape' => false, 'debug' => true]
+--EXPECT--
+b
+string(1) "b"
diff --git a/test/Twig/Tests/IntegrationTest.php b/test/Twig/Tests/IntegrationTest.php
index be25047c8..3d9a14cdd 100644
--- a/test/Twig/Tests/IntegrationTest.php
+++ b/test/Twig/Tests/IntegrationTest.php
@@ -34,7 +34,7 @@ class Twig_Tests_IntegrationTest extends IntegrationTestCase
 {
     public function getExtensions()
     {
-        $policy = new SecurityPolicy([], [], [], [], []);
+        $policy = new SecurityPolicy([], [], [], [], ['dump']);
 
         return [
             new DebugExtension(),