Unable to uncheck checkbox with postback

I've got several checkboxes which are used to hide and unhide asp.net panels, I've done this using C# which is why I needed the postback.

Now initially the panels are hidden and my code works fine when checked, but when I try to uncheck them they retain their values after postback and the panels are still visible.

Here's my code:

Markup:

<asp:CheckBox ID="cbxHideShow" runat="server" AutoPostBack="true" OnCheckedChanged="cbxHideShow_CheckedChanged" Text="Hide/Show Panel"/>

and code-behind:

protected void cbxHideShow_CheckedChanged(object sender, EventArgs e)
{
    if (cbxHideShow.Checked = true)
    {
        Panel1.Visible = true;
    }
    else
    {
        Panel1.Visible = false;
    }
}

If someone could let me know what I'm doing wrong I would very much appreciate it.