Problém s SESSIONS

...
<form action="login.php" method="post">
Jméno<br />
<input type="text" name="loginname" /><br />
Heslo<br />
<input type="password" name="password" /><br />
<input type="submit" value="Přihlásit" />      
</form>
...

<?php
session_start();

$loginname = $_POST["loginname"];
$password = $_POST["password"];

if ($loginname=="adminsk" && $password=="w4uh3") {
$_SESSION["admin"]==1;
header("Location: admin.php");
}
else {
header("Location: index.php?err");
}
?>

<?php
require_once("connset.php");
session_start();
if ($_SESSION["admin"]==1) {
echo "It's OK";
}
else {
header("Location: index.php");
}
?>