Unable to declare to use C++11 in CLion

For hours I'm trying to declare to use C++11 in CLion without any effects. Still CLion shows me undefined functions name that actually exist, but in C++11:

.

My CMakeLists.txt files looks like:

cmake_minimum_required(VERSION 3.6)
project(Program)

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -pthread")

add_executable(program src/program.cpp)

How am I doing wrong?