diff --git a/framework/CHANGELOG.md b/framework/CHANGELOG.md
index 1e56a2b6e8..9332ca080a 100644
--- a/framework/CHANGELOG.md
+++ b/framework/CHANGELOG.md
@@ -4,6 +4,7 @@ Yii Framework 2 Change Log
 2.0.33 under development
 ------------------------
 
+- Bug #17843: Fix `yii\web\Session::setCookieParamsInternal` check param "samesite" (schevgeny)
 - Bug #17828: Fix `yii\web\UploadedFile::saveAs()` failing when error value in `$_FILES` entry is a string (haveyaseen)
 - Bug #17829: `yii\helpers\ArrayHelper::filter` now correctly filters data when passing a filter with more than 2 levels (rhertogh)
 
diff --git a/framework/web/Session.php b/framework/web/Session.php
index b59c47995a..4c0c9e537b 100644
--- a/framework/web/Session.php
+++ b/framework/web/Session.php
@@ -398,8 +398,8 @@ class Session extends Component implements \IteratorAggregate, \ArrayAccess, \Co
             if (PHP_VERSION_ID >= 70300) {
                 session_set_cookie_params($data);
             } else {
-                if (!empty($data['sameSite'])) {
-                    throw new InvalidConfigException('sameSite cookie is not supported by PHP versions < 7.3.0 (set it to null in this environment)');
+                if (!empty($data['samesite'])) {
+                    throw new InvalidConfigException('samesite cookie is not supported by PHP versions < 7.3.0 (set it to null in this environment)');
                 }
                 session_set_cookie_params($data['lifetime'], $data['path'], $data['domain'], $data['secure'], $data['httponly']);
             }