diff --git a/core/modules/system/tests/modules/theme_test/theme_test.module b/core/modules/system/tests/modules/theme_test/theme_test.module
index f2cd4a0..265cf80 100644
--- a/core/modules/system/tests/modules/theme_test/theme_test.module
+++ b/core/modules/system/tests/modules/theme_test/theme_test.module
@@ -14,6 +14,9 @@ function theme_test_theme($existing, $type, $theme, $path) {
   $items['theme_test_template_test_2'] = array(
     'template' => 'theme_test.template_test',
   );
+  $items['theme_test_foo'] = array(
+    'variables' => array('foo' => NULL),
+  );
   return $items;
 }
 
@@ -142,3 +145,10 @@ function theme_test_preprocess_html(&$variables) {
   $variables['html_attributes_array']['theme_test_html_attribute'] = 'theme test html attribute value';
   $variables['body_attributes_array']['theme_test_body_attribute'] = 'theme test body attribute value';
 }
+
+/**
+ * Theme function for testing theme('theme_test_foo').
+ */
+function theme_theme_test_foo($variables) {
+  return $variables['foo'];
+}
diff --git a/core/modules/system/tests/theme.test b/core/modules/system/tests/theme.test
index 978887c..423ee71 100644
--- a/core/modules/system/tests/theme.test
+++ b/core/modules/system/tests/theme.test
@@ -154,6 +154,19 @@ class ThemeUnitTest extends DrupalWebTestCase {
     $this->assertNotEqual(theme_get_setting('subtheme_override', 'test_basetheme'), theme_get_setting('subtheme_override', 'test_subtheme'), t('Base theme\'s default settings values can be overridden by subtheme.'));
     $this->assertIdentical(theme_get_setting('basetheme_only', 'test_subtheme'), 'base theme value', t('Base theme\'s default settings values are inherited by subtheme.'));
   }
+
+  /**
+   * Ensures the theme registry is rebuilt when modules are disabled/enabled.
+   */
+  function testRegistryRebuild() {
+    $this->assertIdentical(theme('theme_test_foo', array('foo' => 'a')), 'a', 'The theme registry contains theme_test_foo.');
+
+    module_disable(array('theme_test'), FALSE);
+    $this->assertIdentical(theme('theme_test_foo', array('foo' => 'b')), '', 'The theme registry does not contain theme_test_foo, because the module is disabled.');
+
+    module_enable(array('theme_test'), FALSE);
+    $this->assertIdentical(theme('theme_test_foo', array('foo' => 'c')), 'c', 'The theme registry contains theme_test_foo again after re-enabling the module.');
+  }
 }
 
 /**