Public Folder Migration Error

So when I tried to migrate public folders from Exchange 2007 to 2013, I encountered the following error:

Error: Property expression "xxx xxx" isn't valid.

It appears that for some reason, some mail enabled Public Folders had Alias properties with blanks in them. As we all know, blank or spaces are not allowed in Alias field.

The easiest way to fix this is to launch Public Folder Management Console (from mmc.exe, add snap-in), locate all mail enabled public folder and correct the Alias field.