diff --git a/CHANGELOG b/CHANGELOG
index dd75bcaab..7d722557a 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -218,6 +218,7 @@
 
 * 1.40.0 (2019-XX-XX)
 
+ * allowed Twig\NodeVisitor\NodeVisitorInterface::leaveNode() to return "null" instead of "false" (same meaning)
  * added the "apply" tag as a replacement for the "filter" tag
  * allowed Twig\Loader\FilesystemLoader::findTemplate() to return "null" instead of "false" (same meaning)
  * added support for "Twig\Markup" instances in the "in" test
diff --git a/src/NodeTraverser.php b/src/NodeTraverser.php
index e48a7b0f2..3d1d74703 100644
--- a/src/NodeTraverser.php
+++ b/src/NodeTraverser.php
@@ -65,7 +65,7 @@ final class NodeTraverser
         $node = $visitor->enterNode($node, $this->env);
 
         foreach ($node as $k => $n) {
-            if (false !== $m = $this->traverseForVisitor($visitor, $n)) {
+            if (false !== ($m = $this->traverseForVisitor($visitor, $n)) && null !== $m) {
                 if ($m !== $n) {
                     $node->setNode($k, $m);
                 }
diff --git a/src/NodeVisitor/AbstractNodeVisitor.php b/src/NodeVisitor/AbstractNodeVisitor.php
index c11933518..d1b0d1458 100644
--- a/src/NodeVisitor/AbstractNodeVisitor.php
+++ b/src/NodeVisitor/AbstractNodeVisitor.php
@@ -17,6 +17,8 @@ use Twig\Node\Node;
 /**
  * Used to make node visitors compatible with Twig 1.x and 2.x.
  *
+ * To be removed in Twig 3.1.
+ *
  * @author Fabien Potencier <fabien@symfony.com>
  */
 abstract class AbstractNodeVisitor implements NodeVisitorInterface
@@ -41,7 +43,7 @@ abstract class AbstractNodeVisitor implements NodeVisitorInterface
     /**
      * Called after child nodes are visited.
      *
-     * @return Node|false The modified node or false if the node must be removed
+     * @return Node|false|null The modified node or null if the node must be removed
      */
     abstract protected function doLeaveNode(Node $node, Environment $env);
 }
diff --git a/src/NodeVisitor/NodeVisitorInterface.php b/src/NodeVisitor/NodeVisitorInterface.php
index 1cd9269fd..9b10eb75f 100644
--- a/src/NodeVisitor/NodeVisitorInterface.php
+++ b/src/NodeVisitor/NodeVisitorInterface.php
@@ -31,7 +31,7 @@ interface NodeVisitorInterface
     /**
      * Called after child nodes are visited.
      *
-     * @return Node|false The modified node or false if the node must be removed
+     * @return Node|false|null The modified node or null if the node must be removed
      */
     public function leaveNode(Node $node, Environment $env);
 
diff --git a/src/TokenParser/AbstractTokenParser.php b/src/TokenParser/AbstractTokenParser.php
index fc8c11a23..2c2f90b7f 100644
--- a/src/TokenParser/AbstractTokenParser.php
+++ b/src/TokenParser/AbstractTokenParser.php
@@ -20,6 +20,9 @@ use Twig\Parser;
  */
 abstract class AbstractTokenParser implements TokenParserInterface
 {
+    /**
+     * @var Parser
+     */
     protected $parser;
 
     public function setParser(Parser $parser)