diff --git a/lib/datalib.php b/lib/datalib.php
index c9f096af696..b5bcd3a5231 100644
--- a/lib/datalib.php
+++ b/lib/datalib.php
@@ -216,7 +216,7 @@ function search_users($courseid, $groupid, $searchtext, $sort='', array $excepti
  *     parameters (using named placeholders).
  */
 function users_search_sql($search, $u = 'u', $searchanywhere = true, array $extrafields = array(),
-        array $exclude = array(), array $includeonly = array()) {
+        array $exclude = null, array $includeonly = null) {
     global $DB, $CFG;
     $params = array();
     $tests = array();
diff --git a/user/selector/lib.php b/user/selector/lib.php
index 1483f6f8276..9692e3bb388 100644
--- a/user/selector/lib.php
+++ b/user/selector/lib.php
@@ -434,7 +434,7 @@ abstract class user_selector_base {
      *      this uses ? style placeholders.
      */
     protected function search_sql($search, $u) {
-        return users_search_sql($search, 'u', $this->searchanywhere, $this->extrafields,
+        return users_search_sql($search, $u, $this->searchanywhere, $this->extrafields,
                 $this->exclude, $this->validatinguserids);
     }