Superassignment (<<-) and indexing

In a clean environment under R-2.1.0 on Linux:

x <- 1:5
x[3] <<- 9

Error: Object "x" not found

Isn't that odd?  (Note x <<- 9 works just fine.)

Why am I doing this?  Because I'm stepping through code that
normally lives inside a function, where "<<-" is appropriate.

-- David Brahm (brahm at alum.mit.edu)