"nullptr" is undefined

I am trying to upgrade ParaView version of my co-processing code from 5.4.1 to 5.6.0. 5.4.1 is fine and compiles without any problem but when i try to use ParaView 5.6.0, i am getting following error

error: identifier “nullptr” is undefined

I also try to compile both my code and also ParaView 5.6.0 with CXXFLAGS="-std=c++11" flag but it does not help. Do I need to include additional header file to my code?

Thanks,

Try compiling with debug turned on, and then run it in a debugger? I believe it should then tell you where this error occurred?