Error message: name lookup of ‘jj’ changed for ISO ‘for’ scoping, (if you use ‘-fpermissive’ G++ will accept your code)

The error is:

In function ‘int returnShortestWeightedBranch(std::vector<route, std::allocator<route> >*)’:
error: name lookup of ‘jj’ changed for ISO ‘for’ scoping
note: (if you use ‘-fpermissive’ G++ will accept your code)

The code is:

for (int i = 0; i< routeVector.size(); i++)
        {
            if (routeVector[i].exitPoint == exitPointDetailsVector[preserveL].exitPoint)
            {
                cout << "\n-----------parent: " << routeVector[i].exitPoint;
                branch obj;
                obj.connectedExitPoint = exitPointDetailsVector[preserveI].exitPoint;
                routeVector[i].selectedBranchesVector.push_back (obj);

                for (int jj = 0; jj < routeVector[i].selectedBranchesVector.size(); jj++);
                {
                    cout << "\n-----------branch: " << routeVector[i].selectedBranchesVector[jj].connectedExitPoint;
                }
            }
        }

What can be the problem here?

EDIT 1:

I changed the following:

for (int jj = 0; jj < routeVector[i].selectedBranchesVector.size(); jj++);

to:

int jj;
for (jj = 0; jj < routeVector[i].selectedBranchesVector.size(); jj++);

and now it is working!! I fail to understand the REASONS.