diff --git a/includes/theme.inc b/includes/theme.inc
index 3287073..f592891 100644
--- a/includes/theme.inc
+++ b/includes/theme.inc
@@ -1902,11 +1902,12 @@ function theme_feed_icon($variables) {
  */
 function theme_html_tag($variables) {
   $element = $variables['element'];
+  $attributes = isset($element['#attributes']) ? drupal_attributes($element['#attributes']) : '';
   if (!isset($element['#value'])) {
-    return '<' . $element['#tag'] . drupal_attributes($element['#attributes']) . " />\n";
+    return '<' . $element['#tag'] . $attributes . " />\n";
   }
   else {
-    $output = '<' . $element['#tag'] . drupal_attributes($element['#attributes']) . '>';
+    $output = '<' . $element['#tag'] . $attributes . '>';
     if (isset($element['#value_prefix'])) {
       $output .= $element['#value_prefix'];
     }
diff --git a/modules/simpletest/tests/theme.test b/modules/simpletest/tests/theme.test
index f1e1bd5..11432f7 100644
--- a/modules/simpletest/tests/theme.test
+++ b/modules/simpletest/tests/theme.test
@@ -354,3 +354,37 @@ class ThemeFastTestCase extends DrupalWebTestCase {
     $this->assertText('registry not initialized', t('The registry was not initialized'));
   }
 }
+
+/**
+ * Unit tests for theme_html_tag().
+ */
+class ThemeHtmlTag extends DrupalUnitTestCase {
+  public static function getInfo() {
+    return array(
+      'name' => 'Theme HTML Tag',
+      'description' => 'Tests theme_html_tag() built-in theme functions.',
+      'group' => 'Theme',
+    );
+  }
+
+  /**
+   * Test function theme_html_tag()
+   */
+  function testThemeHtmlTag() {
+    // Test auto-closure br tag
+    $tag['element'] = array('#tag' => 'br');
+    $this->assertEqual('<br />'."\n", theme_html_tag($tag), t('Test auto-closure for br tag.'));
+
+    // Test auto-closure hr tag with attributes
+    $tag['element'] = array('#tag' => 'hr', '#attributes' => array('class' => 'class1'));
+    $this->assertEqual('<hr class="class1" />'."\n", theme_html_tag($tag), t('Test auto-closure for hr tag with a class.'));
+
+    // Test p tag with value
+    $tag['element'] = array('#tag' => 'p', '#value' => 'test');
+    $this->assertEqual('<p>test</p>'."\n", theme_html_tag($tag), t('Test p tag generation.'));
+
+    // Test h2 tag with value and attributes
+    $tag['element'] = array('#tag' => 'h2', '#value' => 'title test', '#attributes' => array('title' => 'title h2'));
+    $this->assertEqual('<h2 title="title h2">title test</h2>'."\n", theme_html_tag($tag), t('Test h2 tag generation with title attribute.'));
+  }
+}