IDE don't find header file

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Hello,

I'm using qtcreator 3.4.2 with ROS groovy

I have a problem with finding a few header files inside my IDE. But building runs well.

I tried the same setup without catkin

#include <iostream>
#include "json/json.h"

int main()
{
  std::cout << "hello include \n";
  return 0;
}

CMakeLists.txt

INCLUDE_DIRECTORIES(${CMAKE_CURRENT_LIST_DIR}/common/third_party)
add_executable(main main.cpp)

If I integrate this the IDE find my json.h

If I integrate the same in my package, the IDE tells me that the header is not found. But i can build without Problems. Anyone has an idea why QTcreator don't find this header if I use catkin?