C++ std::map on header not working - ´map´ in namespace ´std´ does not name a type

Here is my C++ header file:

class MyClass { 

public: 
    std::map<std::string, std::string> dictionary;

}

I´m getting the following error on compilation for that line:

error: 'map' in namespace 'std' does not name a type

I´m using the c++11 style, configured in Eclipse. I´m running in Ubuntu.

Please help me to solve that...