diff --git a/mod/assign/externallib.php b/mod/assign/externallib.php
index 6924aad7e0b96..32c3e5597c1f5 100644
--- a/mod/assign/externallib.php
+++ b/mod/assign/externallib.php
@@ -2316,7 +2316,7 @@ public static function get_submission_status_parameters() {
                 'assignid' => new external_value(PARAM_INT, 'assignment instance id'),
                 'userid' => new external_value(PARAM_INT, 'user id (empty for current user)', VALUE_DEFAULT, 0),
                 'groupid' => new external_value(PARAM_INT, 'filter by users in group (used for generating the grading summary).
-                    Empty or 0 for all groups information.', VALUE_DEFAULT, 0),
+                    0 for all groups information, any other empty value will calculate currrent group.', VALUE_DEFAULT, 0),
             )
         );
     }
@@ -2368,8 +2368,9 @@ public static function get_submission_status($assignid, $userid = 0, $groupid =
                 throw new moodle_exception('notingroup');
             }
         } else {
-            // A null gorups means that following functions will calculate the current group.
-            $groupid = null;
+            // A null group means that following functions will calculate the current group.
+            // A groupid set to 0 means all groups.
+            $groupid = ($params['groupid'] == 0) ? 0 : null;
         }
         if ($assign->can_view_grades($groupid)) {
             $gradingsummary = $assign->get_assign_grading_summary_renderable($groupid);
diff --git a/mod/assign/tests/externallib_test.php b/mod/assign/tests/externallib_test.php
index c038b55fa7359..a152bbd768a88 100644
--- a/mod/assign/tests/externallib_test.php
+++ b/mod/assign/tests/externallib_test.php
@@ -2133,6 +2133,7 @@ public function test_get_submission_status_in_submission_status() {
      * Test get_submission_status using the teacher role.
      */
     public function test_get_submission_status_in_submission_status_for_teacher() {
+        global $DB;
         $this->resetAfterTest(true);
 
         list($assign, $instance, $student1, $student2, $teacher, $g1, $g2) = $this->create_submission_for_testing_status(true);
@@ -2166,11 +2167,22 @@ public function test_get_submission_status_in_submission_status_for_teacher() {
         $this->assertEquals(0, $result['gradingsummary']['submissionssubmittedcount']); // G2 students didn't submit yet.
         $this->assertEquals(0, $result['gradingsummary']['submissionsneedgradingcount']);   // G2 students didn't submit yet.
 
-        // Should return also 1 participant if we allow the function to auto-select the group.
+        // Should not return information for all users (missing access to all groups capability for non-editing teacher).
         $result = mod_assign_external::get_submission_status($assign->get_instance()->id);
         $result = external_api::clean_returnvalue(mod_assign_external::get_submission_status_returns(), $result);
         $this->assertCount(0, $result['warnings']);
-        $this->assertEquals(1, $result['gradingsummary']['participantcount']);
+        $this->assertFalse(isset($result['gradingsummary']));
+
+        // Should return all participants if we grant accessallgroups capability to the normal teacher role.
+        $context = context_course::instance($assign->get_instance()->course);
+        $teacherrole = $DB->get_record('role', array('shortname' => 'teacher'));
+        assign_capability('moodle/site:accessallgroups', CAP_ALLOW, $teacherrole->id, $context->id, true);
+        accesslib_clear_all_caches_for_unit_testing();
+
+        $result = mod_assign_external::get_submission_status($assign->get_instance()->id);
+        $result = external_api::clean_returnvalue(mod_assign_external::get_submission_status_returns(), $result);
+        $this->assertCount(0, $result['warnings']);
+        $this->assertEquals(2, $result['gradingsummary']['participantcount']);
         $this->assertEquals(0, $result['gradingsummary']['submissiondraftscount']);
         $this->assertEquals(1, $result['gradingsummary']['submissionssubmittedcount']); // One student from G1 submitted.
         $this->assertEquals(1, $result['gradingsummary']['submissionsneedgradingcount']); // One student from G1 submitted.