diff --git a/lib/Cleantalk/ApbctWP/Variables/AltSessions.php b/lib/Cleantalk/ApbctWP/Variables/AltSessions.php
index 9e68edeb3..b46b1628d 100644
--- a/lib/Cleantalk/ApbctWP/Variables/AltSessions.php
+++ b/lib/Cleantalk/ApbctWP/Variables/AltSessions.php
@@ -54,9 +54,9 @@ class AltSessions
 
     public static function getID()
     {
+        // Accept-Language is omitted: XHR and document POST often send different headers.
         $id = Helper::ipGet()
-              . Server::getString('HTTP_USER_AGENT')
-              . Server::getString('HTTP_ACCEPT_LANGUAGE');
+              . Server::getString('HTTP_USER_AGENT');
 
         return substr(hash('sha256', $id), -16);
     }
diff --git a/tests/ApbctWP/Variables/TestAltSessionsGetID.php b/tests/ApbctWP/Variables/TestAltSessionsGetID.php
new file mode 100644
index 000000000..f312873b9
--- /dev/null
+++ b/tests/ApbctWP/Variables/TestAltSessionsGetID.php
@@ -0,0 +1,69 @@
+<?php
+
+namespace ApbctWP\Variables;
+
+use Cleantalk\ApbctWP\Variables\AltSessions;
+use Cleantalk\ApbctWP\Variables\Server;
+use PHPUnit\Framework\TestCase;
+
+class TestAltSessionsGetID extends TestCase
+{
+    /**
+     * @var array
+     */
+    private $serverBackup = array();
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        $this->serverBackup = $_SERVER;
+        Server::getInstance()->variables = array();
+
+        $_SERVER['HTTP_USER_AGENT'] = 'phpunit-user-agent';
+        $_SERVER['REMOTE_ADDR'] = '127.0.0.1';
+    }
+
+    protected function tearDown(): void
+    {
+        $_SERVER = $this->serverBackup;
+        Server::getInstance()->variables = array();
+
+        parent::tearDown();
+    }
+
+    public function testGetIDIgnoresAcceptLanguage()
+    {
+        $_SERVER['HTTP_ACCEPT_LANGUAGE'] = 'en-US';
+        $short = AltSessions::getID();
+
+        Server::getInstance()->variables = array();
+        $_SERVER['HTTP_ACCEPT_LANGUAGE'] = 'en-US,en;q=0.9';
+        $full = AltSessions::getID();
+
+        Server::getInstance()->variables = array();
+        $_SERVER['HTTP_ACCEPT_LANGUAGE'] = 'de-DE,de;q=0.9';
+        $other = AltSessions::getID();
+
+        Server::getInstance()->variables = array();
+        unset($_SERVER['HTTP_ACCEPT_LANGUAGE']);
+        $empty = AltSessions::getID();
+
+        $this->assertSame($short, $full);
+        $this->assertSame($short, $other);
+        $this->assertSame($short, $empty);
+        $this->assertSame(16, strlen($short));
+    }
+
+    public function testGetIDDiffersWhenUserAgentDiffers()
+    {
+        $_SERVER['HTTP_ACCEPT_LANGUAGE'] = 'en-US,en;q=0.9';
+        $first = AltSessions::getID();
+
+        Server::getInstance()->variables = array();
+        $_SERVER['HTTP_USER_AGENT'] = 'phpunit-user-agent-other';
+        $second = AltSessions::getID();
+
+        $this->assertNotSame($first, $second);
+    }
+}