diff --git a/includes/database/mysql/database.inc b/includes/database/mysql/database.inc
index 0d9158789bbadd196172444fd7b7fa8ed4b661ae..7d5d85998dbd53bafcf5458458c5c18bc96f1dc7 100644
--- a/includes/database/mysql/database.inc
+++ b/includes/database/mysql/database.inc
@@ -60,8 +60,10 @@ public function __construct(array $connection_options = array()) {
     // This allows Drupal to run almost seamlessly on many different
     // kinds of database systems. These settings force MySQL to behave
     // the same as postgresql, or sqlite in regards to syntax interpretation
-    // and invalid data handling. See http://drupal.org/node/344575 for further discussion.
-    $this->exec("SET sql_mode='ANSI,TRADITIONAL'");
+    // and invalid data handling. See http://drupal.org/node/344575 for
+    // further discussion. Also, as MySQL 5.5 changed the meaning of
+    // TRADITIONAL we need to spell out the modes one by one.
+    $this->exec("SET sql_mode='ANSI,STRICT_TRANS_TABLES,STRICT_ALL_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER'");
   }
 
   public function queryRange($query, $from, $count, array $args = array(), array $options = array()) {