No C code highlighting in C-projects and files

When I edit C project in QtCreator it still uses c++ code highlighting.
Even when I create project via New-Other-Non-Qt-Plain C application.

The macro __cplusplus is defined, words bool, virtual, template, namespace etc are highlighted as keywords, which brakes syntax. In every C file, despite the project kind.

No matter if I choose clang code model, it still uses c++ code rules.

QtCreator 3.5.1 (from Ubuntu 16.04 repo), Qt 5.5.1