diff -u b/core/lib/Drupal/Core/Render/ProtectedRenderArray.php b/core/lib/Drupal/Core/Render/ProtectedRenderArray.php
--- b/core/lib/Drupal/Core/Render/ProtectedRenderArray.php
+++ b/core/lib/Drupal/Core/Render/ProtectedRenderArray.php
@@ -25,6 +25,35 @@
   }
 
   /**
+   * Determines if a given array is a render array.
+   *
+   * @param mixed $input
+   *   A variable that may be a render array.
+   *
+   * @return boolean
+   *   Whether or not the given array is a render array.
+   */
+  public static function isRenderArray($input) {
+    if (!is_array($input)) {
+      return FALSE;
+    }
+    // Recurse over all keys in the array to determine if any are properties.
+    // This is done as the render system allows deeply nested arrays that may
+    // not contain property keys in the first few levels.
+    $iterator = new \RecursiveArrayIterator($input);
+    $recursive = new \RecursiveIteratorIterator(
+      $iterator,
+      \RecursiveIteratorIterator::SELF_FIRST
+    );
+    foreach ($recursive as $key => $value) {
+      if (Element::property($key)) {
+        return TRUE;
+      }
+    }
+    return FALSE;
+  }
+
+  /**
    * {@inheritdoc}
    */
   public function toRenderable() {
@@ -48,7 +77,7 @@
    */
   public function offsetGet($index) {
     $value = parent::offsetGet($index);
-    if (is_array($value) && !empty($value)) {
+    if (self::isRenderArray($value)) {
       $value = new ProtectedRenderArray($value);
     }
     return $value;
diff -u b/core/lib/Drupal/Core/Render/ProtectedRenderArrayIterator.php b/core/lib/Drupal/Core/Render/ProtectedRenderArrayIterator.php
--- b/core/lib/Drupal/Core/Render/ProtectedRenderArrayIterator.php
+++ b/core/lib/Drupal/Core/Render/ProtectedRenderArrayIterator.php
@@ -19,7 +19,7 @@
    */
   public function offsetGet($index) {
     $value = parent::offsetGet($index);
-    if (is_array($value) && !empty($value)) {
+    if (ProtectedRenderArray::isRenderArray($value)) {
       $value = new ProtectedRenderArray($value);
     }
     return $value;
@@ -30,7 +30,7 @@
    */
   public function current() {
     $value = parent::current();
-    if (is_array($value) && !empty($value)) {
+    if (ProtectedRenderArray::isRenderArray($value)) {
       $value = new ProtectedRenderArray($value);
     }
     return $value;
diff -u b/core/lib/Drupal/Core/Template/TwigEnvironment.php b/core/lib/Drupal/Core/Template/TwigEnvironment.php
--- b/core/lib/Drupal/Core/Template/TwigEnvironment.php
+++ b/core/lib/Drupal/Core/Template/TwigEnvironment.php
@@ -157,7 +157,7 @@
   public function wrapContext(&$context) {
     if (is_array($context)) {
       foreach ($context as $key => $value) {
-        if (is_array($context[$key]) && !empty($context[$key])) {
+        if (ProtectedRenderArray::isRenderArray($context[$key])) {
           $context[$key] = new ProtectedRenderArray($context[$key]);
         }
       }
diff -u b/core/tests/Drupal/Tests/Core/Render/ProtectedRenderArrayTest.php b/core/tests/Drupal/Tests/Core/Render/ProtectedRenderArrayTest.php
--- b/core/tests/Drupal/Tests/Core/Render/ProtectedRenderArrayTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/ProtectedRenderArrayTest.php
@@ -23,6 +23,8 @@
   public function testSubArrayAccess(ProtectedRenderArray $protected_array) {
     $this->assertTrue($protected_array['sub_array'] instanceof ProtectedRenderArray);
     $this->assertTrue($protected_array['sub_array']['sub_sub_array'] instanceof ProtectedRenderArray);
+    $this->assertTrue(is_array($protected_array['sub_non_render_array']));
+    $this->assertTrue($protected_array['sub_odd_array']['foo']['bar'] instanceof ProtectedRenderArray);
   }
 
   /**
@@ -33,9 +35,12 @@
    */
   public function testIteratedSubArrayAccess(ProtectedRenderArray $protected_array) {
     foreach ($protected_array as $key => $value) {
-      if ($key === 'sub_array') {
+      if ($key === 'sub_array' || $key === 'sub_odd_array') {
         $this->assertTrue($value instanceof ProtectedRenderArray);
       }
+      if ($key === 'sub_non_render_array') {
+        $this->assertTrue(is_array($value));
+      }
     }
   }
 
@@ -77,6 +82,20 @@
           'sub_markup' => [
             '#markup' => 'Test',
           ],
+          'sub_non_render_array' => [
+            'foo' => 'bar',
+            'baz',
+          ],
+          // This appears malformed, but is valid to the render system.
+          'sub_odd_array' => [
+            'foo' => [
+              'bar' => [
+                'baz' => [
+                  '#markup' => 'Really, really nested!'
+                ]
+              ],
+            ],
+          ],
         ])
       ],
     ];