How can my private method access public enum in C++?

I would like to know how or if I can make my public enum payloadTypes accessible to my private method threshold() in my following class:

class A {

private: 
    unsigned int  threshold(payloadTypes kindOfPayload,int x,int y);

public:
 enum payloadTypes {
  INVALID =-1,
  TEST=0,
  THRESHOLDS,
  RX,
 };

}

I am getting this error if I do as above, and I don't want to change the scope of my enum to private

error: 'payloadTypes ' has not been declared

unsigned int threshold(payloadTypes kindOfPayload,int x,int y);