I know this is very old, but I ran into the same problem and could not find a solution online, so I'm hopefully going to save someone else the trouble in the future.

The problem is that you are missing either "_x86_" (for 32 bit) or "_AMD64" (for 64 bit) in your "DEFINES" variable. Additionally, in my case I ended up having to remove a few extra defines that Qt put in automatically. Here's how I fixed this issue in my .pro file:

Qt Code: 
  1. DEFINES += _AMD64_
  2. DEFINES -= WIN32 WIN64
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Hope this helps.