There was a new Steam beta released today, and it looks like this is now fixed up. I've tested it myself and the installation worked great. Could you try it out now and let me know how it works out? Here are the steps again if needed:
Go to Steam > Settings > Account
In the "Beta participation" section, click the "Change" button
Choose "Steam Beta update" from the drop-down, then click OK
Click OK again, and you should get prompted to restart Steam to install the new beta
