Setting Masterpage and Theme in the same Web iteration

I have an interesting issue within a Branding Feature. I'm iterating through all Webs and setting the Theme and the MasterPage.

Setting the master page works by itself:

foreach(SPWeb web in site.AllWebs)
{
    web.MasterUrl = masterUrl;
    web.Update();
}

Setting the theme also works by itself:

foreach(SPWeb web in site.AllWebs)
{
    web.ApplyTheme(themeUrl, "", "", true);
}

But together it throws the error (on web.update()) "the web being updated was changed by an external process."

foreach(SPWeb web in site.AllWebs)
{
    web.ApplyTheme(themeUrl, "", "", true);
    web.MasterUrl = masterUrl;
    web.Update();
}