diff --git a/backup/moodle2/restore_stepslib.php b/backup/moodle2/restore_stepslib.php
index 4a4b1badabf..db7740a58a6 100644
--- a/backup/moodle2/restore_stepslib.php
+++ b/backup/moodle2/restore_stepslib.php
@@ -323,7 +323,8 @@ class restore_gradebook_structure_step extends restore_structure_step {
 
         // We need to update the calculations for calculated grade items that may reference old
         // grade item ids using ##gi\d+##.
-        list($sql, $params) = $DB->get_in_or_equal(array_values($mappings), SQL_PARAMS_NAMED);
+        // $mappings can be empty, use 0 if so (won't match ever)
+        list($sql, $params) = $DB->get_in_or_equal(array_values($mappings), SQL_PARAMS_NAMED, 'param', true, 0);
         $sql = "SELECT gi.id, gi.calculation
                   FROM {grade_items} gi
                  WHERE gi.id {$sql} AND