diff --git a/lib/tests/grades_externallib_test.php b/lib/tests/grades_externallib_test.php
index 866ac32b354..eb5a39255bc 100644
--- a/lib/tests/grades_externallib_test.php
+++ b/lib/tests/grades_externallib_test.php
@@ -284,6 +284,7 @@ class core_grades_external_testcase extends externallib_advanced_testcase {
             array(),
             array('hidden' => 1)
         );
+        $result = external_api::clean_returnvalue(core_grades_external::update_grades_returns(), $result);
         $this->assertTrue($result == GRADE_UPDATE_OK);
 
         // Check it's definitely hidden.
@@ -409,6 +410,7 @@ class core_grades_external_testcase extends externallib_advanced_testcase {
             array(),
             array('grademax' => $changedmax)
         );
+        $result = external_api::clean_returnvalue(core_grades_external::update_grades_returns(), $result);
         $this->assertTrue($result == GRADE_UPDATE_OK);
         $grades = grade_get_grades($course->id, 'mod', 'assign', $assignment->id);
         $this->assertTrue($grades->items[0]->grademax == $changedmax);
@@ -423,6 +425,7 @@ class core_grades_external_testcase extends externallib_advanced_testcase {
             0,
             array(array('studentid' => $student1->id, 'grade' => $student1grade))
         );
+        $result = external_api::clean_returnvalue(core_grades_external::update_grades_returns(), $result);
         $this->assertTrue($result == GRADE_UPDATE_OK);
         $grades = grade_get_grades($course->id, 'mod', 'assign', $assignment->id, array($student1->id));
         $this->assertTrue($grades->items[0]->grades[$student1->id]->grade == $student1grade);
@@ -441,6 +444,7 @@ class core_grades_external_testcase extends externallib_advanced_testcase {
                 array('studentid' => $student2->id, 'grade' => $student2grade)
             )
         );
+        $result = external_api::clean_returnvalue(core_grades_external::update_grades_returns(), $result);
         $this->assertTrue($result == GRADE_UPDATE_OK);
         $grades = grade_get_grades($course->id, 'mod', 'assign', $assignment->id, array($student1->id, $student2->id));
         $this->assertTrue($grades->items[0]->grades[$student1->id]->grade == $student1grade);
@@ -516,6 +520,7 @@ class core_grades_external_testcase extends externallib_advanced_testcase {
             array(),
             array('hidden' => 1)
         );
+        $result = external_api::clean_returnvalue(core_grades_external::update_grades_returns(), $result);
         $this->assertTrue($result == GRADE_UPDATE_OK);
         $grades = grade_get_grades($course->id, 'mod', 'assign', $assignment->id);
         $this->assertTrue($grades->items[0]->hidden == 1);