Usage of memcpy()

I've got this situation (uVision3 V3.02):

Memory config:
- RAM at 0x10000-0x20000
- Reserved area: 0x10000-0x10010

When using memcpy in this way:

unsigned char an_array[10] = "12345";

memcpy((void*)0x10000,an_array,5);

when I run this in the debugger, every time a value from the array is written to the specified area, the message: "memory access violation at <address>" is given.

Why is this? I reserved the memory right?

- Dirk