diff --git a/lib/dml/mssql_native_moodle_database.php b/lib/dml/mssql_native_moodle_database.php
index 323a2fe3c57b9..db1e00d0dbe63 100644
--- a/lib/dml/mssql_native_moodle_database.php
+++ b/lib/dml/mssql_native_moodle_database.php
@@ -1176,7 +1176,7 @@ public function sql_like($fieldname, $param, $casesensitive = true, $accentsensi
     public function sql_concat() {
         $arr = func_get_args();
         foreach ($arr as $key => $ele) {
-            $arr[$key] = ' CAST(' . $ele . ' AS VARCHAR(255)) ';
+            $arr[$key] = ' CAST(' . $ele . ' AS NVARCHAR(255)) ';
         }
         $s = implode(' + ', $arr);
         if ($s === '') {