diff --git a/admin/tool/cohortroles/classes/api.php b/admin/tool/cohortroles/classes/api.php
index b3f0e541e0538..e94710feb1094 100644
--- a/admin/tool/cohortroles/classes/api.php
+++ b/admin/tool/cohortroles/classes/api.php
@@ -222,6 +222,48 @@ public static function sync_all_cohort_roles() {
             }
         }
 
+        // Clean the legacy role assignments which are stale.
+        $paramsclean['usercontext'] = CONTEXT_USER;
+        $paramsclean['component'] = 'tool_cohortroles';
+        $sql = 'SELECT DISTINCT(ra.id), ra.roleid, ra.userid, ra.contextid, ctx.instanceid
+                  FROM {role_assignments} ra
+                  JOIN {context} ctx ON ctx.id = ra.contextid AND ctx.contextlevel = :usercontext
+                  JOIN {cohort_members} cm ON cm.userid = ctx.instanceid
+                  LEFT JOIN {tool_cohortroles} tc ON tc.cohortid = cm.cohortid
+                    AND tc.userid = ra.userid
+                    AND tc.roleid = ra.roleid
+                 WHERE ra.component = :component
+                   AND tc.id is null';
+        if ($candidatelegacyassignments = $DB->get_records_sql($sql, $paramsclean)) {
+            $sql = 'SELECT DISTINCT(ra.id)
+                  FROM {role_assignments} ra
+                  JOIN {context} ctx ON ctx.id = ra.contextid AND ctx.contextlevel = :usercontext
+                  JOIN {cohort_members} cm ON cm.userid = ctx.instanceid
+                  JOIN {tool_cohortroles} tc ON tc.cohortid = cm.cohortid AND tc.userid = ra.userid
+                 WHERE ra.component = :component';
+            if ($currentvalidroleassignments = $DB->get_records_sql($sql, $paramsclean)) {
+                foreach ($candidatelegacyassignments as $candidate) {
+                    if (!array_key_exists($candidate->id, $currentvalidroleassignments)) {
+                        role_unassign($candidate->roleid, $candidate->userid, $candidate->contextid, 'tool_cohortroles');
+                        $rolesremoved[] = array(
+                            'useridassignedto' => $candidate->userid,
+                            'useridassignedover' => $candidate->instanceid,
+                            'roleid' => $candidate->roleid
+                        );
+                    }
+                }
+            } else {
+                foreach ($candidatelegacyassignments as $candidate) {
+                    role_unassign($candidate->roleid, $candidate->userid, $candidate->contextid, 'tool_cohortroles');
+                    $rolesremoved[] = array(
+                        'useridassignedto' => $candidate->userid,
+                        'useridassignedover' => $candidate->instanceid,
+                        'roleid' => $candidate->roleid
+                    );
+                }
+            }
+        }
+
         return array('rolesadded' => $rolesadded, 'rolesremoved' => $rolesremoved);
     }
 
diff --git a/admin/tool/cohortroles/classes/cohort_role_assignment.php b/admin/tool/cohortroles/classes/cohort_role_assignment.php
index 08ac464107621..08255cfb119a3 100644
--- a/admin/tool/cohortroles/classes/cohort_role_assignment.php
+++ b/admin/tool/cohortroles/classes/cohort_role_assignment.php
@@ -103,5 +103,4 @@ protected function validate_cohortid($value) {
 
         return true;
     }
-
 }
diff --git a/admin/tool/cohortroles/tests/api_test.php b/admin/tool/cohortroles/tests/api_test.php
index d276a2f13ed07..9127e5f985708 100644
--- a/admin/tool/cohortroles/tests/api_test.php
+++ b/admin/tool/cohortroles/tests/api_test.php
@@ -50,8 +50,6 @@ class tool_cohortroles_api_testcase extends advanced_testcase {
      * Setup function- we will create a course and add an assign instance to it.
      */
     protected function setUp() {
-        global $DB;
-
         $this->resetAfterTest(true);
 
         // Create some users.
@@ -133,14 +131,36 @@ public function test_delete_cohort_role_assignment_with_invalid_data() {
 
     public function test_delete_cohort_role_assignment() {
         $this->setAdminUser();
-        $params = (object) array(
+        // Create a cohort role assigment.
+        $params = (object) [
             'userid' => $this->userassignto->id,
             'roleid' => $this->roleid,
             'cohortid' => $this->cohort->id
-        );
-        $result = api::create_cohort_role_assignment($params);
-        $worked = api::delete_cohort_role_assignment($result->get('id'));
-        $this->assertTrue($worked);
+        ];
+        $cohortroleassignment = api::create_cohort_role_assignment($params);
+        $sync = api::sync_all_cohort_roles();
+        $rolesadded = [
+            [
+                'useridassignedto' => $this->userassignto->id,
+                'useridassignedover' => $this->userassignover->id,
+                'roleid' => $this->roleid
+            ]
+        ];
+        $expected = [
+            'rolesadded' => $rolesadded,
+            'rolesremoved' => []
+        ];
+        $this->assertEquals($sync, $expected);
+
+        // Delete the cohort role assigment and confirm the roles are removed.
+        $result = api::delete_cohort_role_assignment($cohortroleassignment->get('id'));
+        $this->assertTrue($result);
+        $sync = api::sync_all_cohort_roles();
+        $expected = [
+            'rolesadded' => [],
+            'rolesremoved' => $rolesadded
+        ];
+        $this->assertEquals($expected, $sync);
     }
 
     public function test_list_cohort_role_assignments() {