diff -u b/includes/output.inc b/includes/output.inc
--- b/includes/output.inc
+++ b/includes/output.inc
@@ -145,6 +145,7 @@
  * @see t()
  */
 function dt($string, $args = array()) {
+  $output = NULL;
   if (function_exists('t') && drush_drupal_version() == 7) {
     $output = t($string, $args);
   }
@@ -152,12 +153,16 @@
     if (function_exists('drupal_classloader')) {
       drupal_classloader();
     }
-    $output = t($string, $args);
+    if (function_exists('t')) {
+      $output = t($string, $args);
+    }
   }
-  else if (drush_drupal_version() <= 7 && function_exists('theme')) {
+  else if (function_exists('t') && drush_drupal_version() <= 7 && function_exists('theme')) {
     $output = t($string, $args);
   }
-  else {
+
+  // If Drupal's t() function unavailable.
+  if (is_null($output)) {
     if (!empty($args)) {
       $output = strtr($string, $args);
     }