Compiler Error When Calling Base Constructor when both Base and Derived are Templated With Derived Type Parameter

I am struggling to understand why the following code does not compile:

template <class T>
class Base {
    public:
        Base(int a){}
};
template <class T>
class Derived: public Base<T>  {
    public:
        Derived(int a): Base(a){}
};
int main(){}

On my compiler (gcc 5.4.0 with C++ 11) this outputs the error message

error: class 'Derived<T>' does not have any field named 'Base'
         Derived(int a): Base(a){}

I see that this is somewhat similar to Template base constructor call in member initialization list error, though that test case actually compiles for me while this one does not: The main difference seems to be that both Base and Derived use the same type parameter. Additionally, it compiles fine if I explicitly add the type parameters or I give an explicit scope for base, as in

template <class T>
class Base {
    public:
        Base(int a){}
};

template <class T>
class Derived: public Base<T>  {
    public:
        Derived(int a): Derived::Base(a){}
};

int main(){}

What's going on? Am I misunderstanding when injected class names may be used?