qmake generated Makefile with precompiled header compiles as c instead of c++ on MSVC

When using qmake to generate a Makefile for a project with precompiled headers, it adds the "-TC" option to the pch generation step. If I use qmake to generate a vcproj instead, it generates the file correctly. 

I ran into this when trying to build my own project (http://github.com/leozide/leocad), but there's also a thread on the Qt forums from another user with the same problem: 

https://forum.qt.io/topic/86103/qt-5-10-tries-to-compile-my-precompiled-headers-as-c-instead-of-c-obviously-fails/7

The thread has a simple example showing the problem.