-u flag not working?

[Eric Tiffany]

I am trying to uninstall broken versions of some ports.  But I get this:

[Instance/bin] > uninstall -u libxml2
--->  The following versions of libxml2 are currently installed:
--->    libxml2 @2.6.28_0
--->    libxml2 @2.6.28_1 (active)
--->    libxml2 @2.6.28_2
Error: port uninstall failed: Registry error: Please specify the full
version as recorded in the port registry.

I thought the -u flag would uninstall non-active versions of a port?

ET