diff --git a/modules/simpletest/drupal_web_test_case.php b/modules/simpletest/drupal_web_test_case.php
index d83dbeb..a277c56 100644
--- a/modules/simpletest/drupal_web_test_case.php
+++ b/modules/simpletest/drupal_web_test_case.php
@@ -696,11 +696,16 @@ class DrupalUnitTestCase extends DrupalTestCase {
    * method.
    */
   protected function setUp() {
-    global $conf;
+    global $conf, $language;
 
     // Store necessary current values before switching to the test environment.
     $this->originalFileDirectory = variable_get('file_public_path', conf_path() . '/files');
 
+    // Set to English to prevent exceptions from utf8_truncate() from t()
+    // during install if the current language is not 'en'.
+    // The following array/object conversion is copied from language_default().
+    $language = (object) array('language' => 'en', 'name' => 'English', 'native' => 'English', 'direction' => 0, 'enabled' => 1, 'plurals' => 0, 'formula' => '', 'domain' => '', 'prefix' => '', 'weight' => 0, 'javascript' => '');
+
     // Reset all statics so that test is performed with a clean environment.
     drupal_static_reset();