diff --git a/db/upgrade.php b/db/upgrade.php
index 3c656f5f..fb110052 100644
--- a/db/upgrade.php
+++ b/db/upgrade.php
@@ -500,6 +500,58 @@ function xmldb_plagiarism_turnitin_upgrade($oldversion) {
         upgrade_plugin_savepoint(true, 2021081301, 'plagiarism', 'turnitin');
     }
 
+    if ($oldversion < 2021101800) {
+        // Set userid to be NOT NULL.
+        $table = new xmldb_table('plagiarism_turnitin_users');
+        $index = new xmldb_index('userid', XMLDB_INDEX_UNIQUE, array('userid'));
+        $field = new xmldb_field('userid', XMLDB_TYPE_INTEGER, '10', null, XMLDB_NOTNULL, null, null, 'id');
+        if ($dbman->field_exists($table, $field)) {
+            // Double-check that there is no records with a NULL value.
+            if ($DB->count_records_select('plagiarism_turnitin_users', 'userid IS NULL') == 0) {
+                // Drop and then recreate unique index, otherwise Moodle will throw dependency exception.
+                if ($dbman->index_exists($table, $index)) {
+                    $dbman->drop_index($table, $index);
+                }
+                $dbman->change_field_notnull($table, $field);
+                $dbman->add_index($table, $index);
+            }
+        }
+
+        // Set courseid to be NOT NULL.
+        $table = new xmldb_table('plagiarism_turnitin_courses');
+        $index = new xmldb_index('courseid', XMLDB_INDEX_UNIQUE, array('courseid'));
+        $field = new xmldb_field('courseid', XMLDB_TYPE_INTEGER, '10', null, XMLDB_NOTNULL, null, null, 'id');
+        if ($dbman->field_exists($table, $field)) {
+            // Double-check that there is no records with a NULL value.
+            if ($DB->count_records_select('plagiarism_turnitin_courses', 'courseid IS NULL') == 0) {
+                // Drop and then recreate unique index, otherwise Moodle will throw dependency exception.
+                if ($dbman->index_exists($table, $index)) {
+                    $dbman->drop_index($table, $index);
+                }
+                $dbman->change_field_notnull($table, $field);
+                $dbman->add_index($table, $index);
+            }
+        }
+
+        upgrade_plugin_savepoint(true, 2021101800, 'plagiarism', 'turnitin');
+    }
+
+    if ($oldversion < 2021121600) {
+        $table = new xmldb_table('plagiarism_turnitin_config');
+        // Delete index if exists.
+        $index = new xmldb_index('config_hash', XMLDB_INDEX_UNIQUE, array('config_hash'));
+        if ($dbman->index_exists($table, $index)) {
+            $dbman->drop_index($table, $index);
+        }
+        // Set config_hash to be NOT NULL, also set precision 255.
+        $field = new xmldb_field('config_hash', XMLDB_TYPE_CHAR, '255', null, XMLDB_NOTNULL, null, null, 'value');
+        if ($dbman->field_exists($table, $field)) {
+            $dbman->change_field_notnull($table, $field);
+        }
+
+        upgrade_plugin_savepoint(true, 2021121600, 'plagiarism', 'turnitin');
+    }
+
     return $result;
 }
 
diff --git a/version.php b/version.php
index c0e71b8c..427e2ca1 100644
--- a/version.php
+++ b/version.php
@@ -19,7 +19,7 @@
  * @copyright 2012 iParadigms LLC
  */
 
-$plugin->version = 2021091501;
+$plugin->version = 2021121600;
 $plugin->release = "3.5+";
 $plugin->requires = 2018051700;
 $plugin->component = 'plagiarism_turnitin';