diff --git a/composer.json b/composer.json
index c6d3f76d1..026753537 100644
--- a/composer.json
+++ b/composer.json
@@ -11,7 +11,7 @@
   "require": {
     "php": ">=7.1",
     "firebase/php-jwt": "^5.2",
-    "guzzlehttp/guzzle": "^6.0|^7.0",
+    "guzzlehttp/guzzle": "^6.2|^7.0",
     "guzzlehttp/psr7": "^1.2",
     "psr/http-message": "^1.0",
     "psr/cache": "^1.0"
diff --git a/tests/Auth/Http/ClientFactoryTest.php b/tests/Auth/Http/ClientFactoryTest.php
index a78c23d13..7ff0cd50b 100644
--- a/tests/Auth/Http/ClientFactoryTest.php
+++ b/tests/Auth/Http/ClientFactoryTest.php
@@ -33,7 +33,7 @@ public function testBuildsGuzzleClient()
         $property->setAccessible(true);
         $guzzleClient = $property->getValue($client);
 
-        if (constant(sprintf('%s::MAJOR_VERSION', get_class($guzzleClient)))) {
+        if (defined(sprintf('%s::MAJOR_VERSION', get_class($guzzleClient)))) {
             // Assert Guzzle 7
             $this->assertEquals(7, $guzzleClient::MAJOR_VERSION);
         } else {