diff --git a/composer.json b/composer.json
index 5f40d91..73f3d68 100644
--- a/composer.json
+++ b/composer.json
@@ -40,7 +40,7 @@
     "require-dev": {
         "squizlabs/php_codesniffer": "^3",
         "inpsyde/php-coding-standards": "^0.13",
-        "phpunit/phpunit": "^8"
+        "phpunit/phpunit": "^8.4"
     },
     "autoload": {
         "files": [
diff --git a/tests/cases/unit/Provider/SiteTest.php b/tests/cases/unit/Provider/SiteTest.php
index 85a3465..277eb0e 100644
--- a/tests/cases/unit/Provider/SiteTest.php
+++ b/tests/cases/unit/Provider/SiteTest.php
@@ -137,7 +137,7 @@ public function testDoesNotCreateOnSingleSite()
     {
         Monkey\Functions\when('is_multisite')->justReturn(false);
 
-        $this->expectExceptionMessageRegExp('/multisite/');
+        $this->expectExceptionMessageMatches('/multisite/');
         $this->factoryProvider(Provider\Site::class)();
     }
 }
diff --git a/tests/cases/unit/Provider/UserTest.php b/tests/cases/unit/Provider/UserTest.php
index 538aad8..38e3115 100644
--- a/tests/cases/unit/Provider/UserTest.php
+++ b/tests/cases/unit/Provider/UserTest.php
@@ -275,7 +275,7 @@ public function testGetFailWithLowercaseId()
         $factory = $this->factoryProvider(Provider\User::class);
         $user = $factory();
 
-        $this->expectExceptionMessageRegExp('/WP_User::ID/');
+        $this->expectExceptionMessageMatches('/WP_User::ID/');
 
         $user->get('id');
     }
diff --git a/tests/cases/unit/ProvidersInitTest.php b/tests/cases/unit/ProvidersInitTest.php
index 652ecf4..29ea6f1 100644
--- a/tests/cases/unit/ProvidersInitTest.php
+++ b/tests/cases/unit/ProvidersInitTest.php
@@ -20,7 +20,7 @@ class ProvidersInitTest extends TestCase
 {
     public function testWpMethodRequiresInitialization()
     {
-        $this->expectExceptionMessageRegExp('/initialized/');
+        $this->expectExceptionMessageMatches('/initialized/');
 
         $provider = new Providers(Factory::create());
         $provider->wp();
@@ -28,7 +28,7 @@ public function testWpMethodRequiresInitialization()
 
     public function testCallMethodRequiresInitialization()
     {
-        $this->expectExceptionMessageRegExp('/initialized/');
+        $this->expectExceptionMessageMatches('/initialized/');
 
         $provider = new Providers(Factory::create());
         /** @noinspection PhpUndefinedMethodInspection */