diff --git a/lib/db/upgrade.php b/lib/db/upgrade.php
index df8786ab514..f2caa411b42 100644
--- a/lib/db/upgrade.php
+++ b/lib/db/upgrade.php
@@ -1583,6 +1583,8 @@ function xmldb_main_upgrade($oldversion) {
     }
 
     if ($oldversion < 2013021100.01) {
+        // Make sure there are no bogus nulls in old MySQL tables.
+        $DB->set_field_select('user', 'password', '', "password IS NULL");
 
         // Changing precision of field password on table user to (255).
         $table = new xmldb_table('user');