diff --git a/completion/classes/external.php b/completion/classes/external.php
index 24384e9ee6d..d92fdaf15e2 100644
--- a/completion/classes/external.php
+++ b/completion/classes/external.php
@@ -249,8 +249,6 @@ class core_completion_external extends external_api {
 
         $completion = new completion_info($course);
         $activities = $completion->get_activities();
-        $progresses = $completion->get_progress_all('u.id = :uid', ['uid' => $params['userid']]);
-        $userprogress = $progresses[$user->id];
 
         $results = array();
         foreach ($activities as $activity) {
@@ -260,26 +258,17 @@ class core_completion_external extends external_api {
                 continue;
             }
 
-            // Get progress information and state.
-            if (array_key_exists($activity->id, $userprogress->progress)) {
-                $thisprogress  = $userprogress->progress[$activity->id];
-                $state         = $thisprogress->completionstate;
-                $timecompleted = $thisprogress->timemodified;
-                $overrideby    = $thisprogress->overrideby;
-            } else {
-                $state = COMPLETION_INCOMPLETE;
-                $timecompleted = 0;
-                $overrideby = null;
-            }
+            // Get progress information and state (we must use get_data because it works for all user roles in course).
+            $activitycompletiondata = $completion->get_data($activity, true, $user->id);
 
             $results[] = array(
                        'cmid'          => $activity->id,
                        'modname'       => $activity->modname,
                        'instance'      => $activity->instance,
-                       'state'         => $state,
-                       'timecompleted' => $timecompleted,
+                       'state'         => $activitycompletiondata->completionstate,
+                       'timecompleted' => $activitycompletiondata->timemodified,
                        'tracking'      => $activity->completion,
-                       'overrideby'    => $overrideby
+                       'overrideby'    => $activitycompletiondata->overrideby
             );
         }
 
diff --git a/completion/tests/externallib_test.php b/completion/tests/externallib_test.php
index 355ecc25de4..cd1e4fa75e9 100644
--- a/completion/tests/externallib_test.php
+++ b/completion/tests/externallib_test.php
@@ -182,6 +182,34 @@ class core_completion_externallib_testcase extends externallib_advanced_testcase
             }
         }
 
+        // Teacher should see his own completion status.
+
+        // Forum complete for teacher.
+        $completion = new completion_info($course);
+        $completion->update_state($cmforum, COMPLETION_COMPLETE);
+
+        $result = core_completion_external::get_activities_completion_status($course->id, $teacher->id);
+        // We need to execute the return values cleaning process to simulate the web service server.
+        $result = external_api::clean_returnvalue(
+            core_completion_external::get_activities_completion_status_returns(), $result);
+
+        // We added 4 activities, but only 3 with completion enabled (one of those is hidden but the teacher can see it).
+        $this->assertCount(3, $result['statuses']);
+
+        $activitiesfound = 0;
+        foreach ($result['statuses'] as $status) {
+            if ($status['cmid'] == $forum->cmid and $status['modname'] == 'forum' and $status['instance'] == $forum->id) {
+                $activitiesfound++;
+                $this->assertEquals(COMPLETION_COMPLETE, $status['state']);
+                $this->assertEquals(COMPLETION_TRACKING_MANUAL, $status['tracking']);
+            } else {
+                $activitiesfound++;
+                $this->assertEquals(COMPLETION_INCOMPLETE, $status['state']);
+                $this->assertEquals(COMPLETION_TRACKING_MANUAL, $status['tracking']);
+            }
+        }
+        $this->assertEquals(3, $activitiesfound);
+
         // Change teacher role capabilities (disable access all groups).
         $context = context_course::instance($course->id);
         assign_capability('moodle/site:accessallgroups', CAP_PROHIBIT, $teacherrole->id, $context);