Destructor called after throwing from a constructor

I used to think that in C++, if a constructor throws an exception, the destructor of this "partially constructed" class is not called.

But it seems that it is not true anymore in C++11: I compiled the following code with g++ and it prints "X destructor" to the console. Why is this?

#include <exception>
#include <iostream>
#include <stdexcept>
using namespace std;

class X
{
public:
    X() : X(10)
    {
        throw runtime_error("Exception thrown in X::X()");    
    }
    X(int a)
    {
        cout << "X::X(" << a << ")" << endl;
    }
    ~X()
    {
        cout << "X destructor" << endl;
    }
};

int main()
{
    try
    {
        X x;
    }
    catch(const exception& e)
    {
        cerr << "*** ERROR: " << e.what() << endl;
    }
}

Output

Standard out:
X::X(10) 
X destructor
Standard error: 
*** ERROR: Exception thrown in X::X()