Class templates changing inheritance behavior

Question

I am trying to create a base class in C++ while using a class template. The class only contains a single protected data member (at least for ease of explaining).

I am then trying to access said data member from a derived class.

This works fine when I am not using templates, however as soon as I implement a template I get the following error:

./main.cpp:45:31: error: use of undeclared identifier 'x'
  void printX(){ std::cout << x << std::endl; }

Usually I would just change my strategy but templates are required for this assignment, and I feel that I have exhausted all other resources at this point.

Any advice on the matter would be greatly appreciated.

Here is the code that generates the error:

#include <iostream>

template <typename T>
class parent{
protected:
  T x;

public: 
  void setX(T a){ x = a; }
};

template <typename T>
class child : public parent<T>{
public: 
  void printX(){ std::cout << x << std::endl; }
};

int main(){
  child<int> obj;
  obj.setX(10); 
  obj.printX();
  return 0;
}