another compiler bug?

[Mitsukai]

i got the folowing code:

unsigned int val1;
void* ptr1 = (void*)val1;
void* ptr2;
ptr1 += ptr2;

then i get the errors:

'+=' : illegal, right operand has type 'void *'
'+=' : pointer on left; needs integral value on right

1. pointers ARE integers.
2. ptr + ptr works why doesnt ptr += ptr?

is the compiler confused because of the int to ptr? (wich i had to type cast, even though pointers are integral)