diff --git a/composer.json b/composer.json
index 07e71bd..99fbd50 100644
--- a/composer.json
+++ b/composer.json
@@ -31,7 +31,7 @@
     "require-dev": {
         "moontoast/math": "^1.1",
         "ircmaxell/random-lib": "^1.1",
-        "phpunit/phpunit": "^4.7|^5.0",
+        "phpunit/phpunit": "^4.7|^5.0|^6.5",
         "squizlabs/php_codesniffer": "^2.3",
         "jakub-onderka/php-parallel-lint": "^0.9.0",
         "mockery/mockery": "^0.9.9",
diff --git a/tests/TestCase.php b/tests/TestCase.php
index 22d9071..3bbf3c6 100644
--- a/tests/TestCase.php
+++ b/tests/TestCase.php
@@ -3,8 +3,9 @@ namespace Ramsey\Uuid\Test;
 
 use AspectMock\Test as AspectMock;
 use Mockery;
+use PHPUnit\Framework\TestCase as PhpUnitTestCase;
 
-class TestCase extends \PHPUnit_Framework_TestCase
+class TestCase extends PhpUnitTestCase
 {
     protected function tearDown()
     {