svn diff with externals

hello all,

this is my first post so apologies if i'm not following etiquette or
anything (feel free to correct me at any time).

anyway, my question has to do with using svn diff (v1.4.3) in the presence
of externally linked files. here's an example of my repo:

- trunk
    - core
    - modules
- branches
    - test1
        - core (svn:externals points to trunk's core folder)
        - modules

let's say i check out test1 and make a change to the file foo.c in core.
from the top of my sandbox, i type "svn diff core/foo.c" and i can see the
diff, everything's fine. however, if i just type "svn diff" without
specifying foo.c (that is, i'm relying on the default recursive behavior),
then nothing shows up. it ignores the diff in the core folder completely.
this seems to only be the case with external files because diffs in the
branch-local modules folder show up fine in both uses of svn diff.

any ideas? is this known behavior? i wasn't able to find anything on this
in the issues mailing list.

thanks in advance for your help!

best,
khang

-- 
khang k tran