ExAllocatePoolWithTag( ) function in the file ntoskrnl_api.c : I changed: WINE_TRACE("(%d %ld %.4s), semi-stub\n", PoolType, NumberOfBytes, (char*)&Tag); to: WINE_TRACE("(%d %ld %4s), semi-stub\n", PoolType, NumberOfBytes, (char*)&Tag); Don't know how decimals are supposed to work with a string, but it didn't work for me.