diff --git a/composer.json b/composer.json
index 9047173367..f010e60485 100644
--- a/composer.json
+++ b/composer.json
@@ -26,7 +26,7 @@
     },
     "require-dev": {
         "friendsofphp/php-cs-fixer": "~2",
-        "phpunit/phpunit": "~4.0 || ~5.0"
+        "phpunit/phpunit": "^4.8.35 || ^5.7"
     },
     "autoload": {
         "psr-4": {
diff --git a/tests/AbstractTestCase.php b/tests/AbstractTestCase.php
index 17e5eb626a..467678a8fb 100644
--- a/tests/AbstractTestCase.php
+++ b/tests/AbstractTestCase.php
@@ -14,9 +14,9 @@
 use Carbon\Carbon;
 use Carbon\CarbonInterval;
 use Closure;
-use PHPUnit_Framework_TestCase;
+use PHPUnit\Framework\TestCase;
 
-abstract class AbstractTestCase extends PHPUnit_Framework_TestCase
+abstract class AbstractTestCase extends TestCase
 {
     /**
      * @var \Carbon\Carbon