class x is hidden by y

[Benjamin Thaut]

For the following code in D 2.0 using dmd 2.049:

import std.stdio;

abstract class foo {
protected:
        void WrongType(){
                assert(0,"Using wrong type");
        }
public:
        void Update(int value){WrongType();}
        void Update(float value){WrongType();}
}

class blup : public foo {
        public override void Update(int value){
                writefln("%s",value);
        }
}

void main(string[] argv){
        foo s = new blup();
        s.Update(2);
        s.Update(2.5f);
}

When compiling with -w option I get the following warning:
test.d(25): Error: class test.blup test.foo.Update(float value) is hidden by 
blup

When compiling without the -w option I get the following runtime error:
core.exception.HiddenFuncError: Hidden method called for test.blup

So I don't get why void Update(float value) is hidden. I come from C++ so
please show me my mistake.

Kind Regards
Benjamin Thaut