diff --git a/includes/common.inc b/includes/common.inc
index dd7e58c3582..3e5d0c383c7 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -3289,12 +3289,10 @@ function drupal_render(&$elements) {
     }
   }
 
-  // Sort the elements by weight, if there are any children, and they have not
-  // been sorted elsewhere already, for example by a database query. Pre-sorted
-  // elements should have $elements['#sorted'] set to TRUE to avoid unnecessary
-  // calls to uasort().
-  $children = !isset($elements['#children']) ? element_children($elements) : FALSE;
-  if (empty($elements['#sorted']) && $children) {
+  // Sort the elements by weight if they have not been sorted elsewhere already,
+  // for example by a database query. Pre-sorted elements should have
+  // $elements['#sorted'] set to TRUE to avoid unnecessary calls to uasort().
+  if (empty($elements['#sorted'])) {
     uasort($elements, 'element_sort');
     $elements['#sorted'] = TRUE;
   }
@@ -3302,6 +3300,7 @@ function drupal_render(&$elements) {
   $content = '';
   $elements += array('#title' => NULL, '#description' => NULL);
   if (!isset($elements['#children'])) {
+    $children = element_children($elements);
     // Render all the children that use a theme function.
     if (isset($elements['#theme']) && empty($elements['#theme_used'])) {
       $elements['#theme_used'] = TRUE;
diff --git a/modules/simpletest/tests/common.test b/modules/simpletest/tests/common.test
index 78dc9f7698b..5f039660f27 100644
--- a/modules/simpletest/tests/common.test
+++ b/modules/simpletest/tests/common.test
@@ -480,6 +480,42 @@ class JavaScriptTestCase extends DrupalWebTestCase {
   }
 }
 
+/**
+ * Tests for drupal_render().
+ */
+class DrupalRenderUnitTestCase extends DrupalWebTestCase {
+  function getInfo() {
+    return array(
+      'name' => t('Drupal render'),
+      'description' => t('Performs unit tests on drupal_render().'),
+      'group' => t('System'),
+    );
+  }
+
+  /**
+   * Test sorting by weight.
+   */
+  function testDrupalRenderSorting() {
+    $first = $this->randomName();
+    $second = $this->randomName();
+    // Build an array with '#weight' set for each element.
+    $elements = array(
+      'second' => array(
+        '#weight' => 10,
+        '#markup' => $second,
+      ),
+      'first' => array(
+        '#weight' => 0,
+        '#markup' => $first,
+      ),
+    );
+    $output = drupal_render($elements);
+    // The lowest weight element should appear last in $output.
+    $this->assertTrue(strpos($output, $second) > strpos($output, $first), t('Elements were sorted correctly by weight'));
+  }
+}
+
+
 /**
  * Tests Drupal error and exception handlers.
  */