diff --git a/src/TwigExtension.php b/src/TwigExtension.php
index 74d1e91..a2d931d 100644
--- a/src/TwigExtension.php
+++ b/src/TwigExtension.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\twig_tweak;
 
+use Drupal\Component\Utility\NestedArray;
 use Drupal\Component\Utility\Unicode;
 use Drupal\Component\Uuid\Uuid;
 use Drupal\Core\Block\BlockPluginInterface;
@@ -720,7 +721,7 @@ class TwigExtension extends \Twig_Extension {
    *
    * @param array $build
    *   The renderable array to add the child item.
-   * @param int|string $key
+   * @param mixed $key
    *   The key of the new element.
    * @param mixed $element
    *   The element to add.
@@ -729,7 +730,12 @@ class TwigExtension extends \Twig_Extension {
    *   The modified array.
    */
   public function with(array $build, $key, $element) {
-    $build[$key] = $element;
+    if (is_array($key)) {
+      NestedArray::setValue($build, $key, $element);
+    }
+    else {
+      $build[$key] = $element;
+    }
     return $build;
   }
 
diff --git a/tests/src/Functional/TwigTweakTest.php b/tests/src/Functional/TwigTweakTest.php
index 4789d69..3ea7115 100644
--- a/tests/src/Functional/TwigTweakTest.php
+++ b/tests/src/Functional/TwigTweakTest.php
@@ -309,6 +309,10 @@ class TwigTweakTest extends BrowserTestBase {
     $xpath = '//div[@class = "tt-with"]/b[text() = "Example"]';
     $this->assertByXpath($xpath);
 
+    // Test nested 'with'.
+    $xpath = '//div[@class = "tt-with-nested" and text() = "{alpha:{beta:{gamma:456}}}"]';
+    $this->assertByXpath($xpath);
+
     // Test 'children'.
     $xpath = '//div[@class = "tt-children" and text() = "doremi"]';
     $this->assertByXpath($xpath);
diff --git a/tests/twig_tweak_test/templates/twig-tweak-test.html.twig b/tests/twig_tweak_test/templates/twig-tweak-test.html.twig
index 759e468..128a768 100644
--- a/tests/twig_tweak_test/templates/twig-tweak-test.html.twig
+++ b/tests/twig_tweak_test/templates/twig-tweak-test.html.twig
@@ -59,6 +59,7 @@
   <div class="tt-check-markup">{{ '<b>bold</b> <strong>strong</strong>' | check_markup('twig_tweak_test') }}</div>
   <div class="tt-truncate">{{ 'Hello world!'|truncate(10, true, true) }}</div>
   <div class="tt-with">{{ {'#markup':'Example'}|with('#prefix', '<b>')|with('#suffix', '</b>') }}</div>
+  <div class="tt-with-nested">{{ {alpha: {beta: {gamma: 123}}}|with(['alpha', 'beta', 'gamma'], 456)|json_encode|replace({'"':''}) }}</div>
   <div class="tt-children">
     {%-
       set build = {