diff --git a/tests/phpunit/auth_plugin_test.php b/tests/phpunit/auth_plugin_test.php
index 647769b..37c588e 100644
--- a/tests/phpunit/auth_plugin_test.php
+++ b/tests/phpunit/auth_plugin_test.php
@@ -44,7 +44,7 @@ class auth_plugin_userkey_testcase extends advanced_testcase {
     /**
      * Initial set up.
      */
-    public function setUp() {
+    public function setUp(): void {
         global $CFG;
 
         require_once($CFG->libdir . "/externallib.php");
diff --git a/tests/phpunit/core_userkey_manager_test.php b/tests/phpunit/core_userkey_manager_test.php
index c95bd6b..bf79ae5 100644
--- a/tests/phpunit/core_userkey_manager_test.php
+++ b/tests/phpunit/core_userkey_manager_test.php
@@ -49,7 +49,7 @@ class core_userkey_manager_testcase extends advanced_testcase {
     /**
      * Initial set up.
      */
-    public function setUp() {
+    public function setUp(): void {
         global $CFG;
 
         parent::setUp();
diff --git a/tests/phpunit/externallib_test.php b/tests/phpunit/externallib_test.php
index 5e29425..79d6e3b 100644
--- a/tests/phpunit/externallib_test.php
+++ b/tests/phpunit/externallib_test.php
@@ -33,7 +33,7 @@ class auth_userkey_externallib_testcase extends advanced_testcase {
     /**
      * Initial set up.
      */
-    public function setUp() {
+    public function setUp(): void {
         global $CFG;
 
         require_once($CFG->libdir . "/externallib.php");