Need a fix for dpkg --print-architecture failure

Hello, i have a dpkg problem. My system:

uname -a
Linux Ubuntu-1004-lucid-64-minimal 2.6.32-35-server #78-Ubuntu SMP Tue Oct 11 16:26:12 UTC 2011 x86_64 GNU/Linux

more /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 26
model name : Intel(R) Core(TM) i7 CPU 920 @ 2.67GHz
(...)

But dpkg --print-architecture returns
amd64

What is the way to fix this?
Best regards.